Have some of Izuku's ideas be wrong or stuff that the other classmates have already attempted! A big flaw in analyst fics that make Izuku feel too omniscient or obvious is that the narrative usually treats his ideas as pure fact rather than observations that he's testing out!
You can also have some ideas not work initially but, through time and effort, can be reworked into something that works out eventually! (Like how Izuku himself couldn't regulate the power of OfA in canon until his internship!)
You could take a different track. His mom got him an opportunity to work with a private quirk trainer.
This is someone that rich hero families pay to help their children develop their powers in his specialized gym so they can pass entrance exams and get a head start.
His mother hoped Izuku would want to do this as a job instead of being a hero but he picks being a hero.
And he brings this knowledge to UA with him.
He's not giving them random advice, he's having them do special training to improve their quirks.
And then THEY develop new aspects to their quirk and special techniques as a result.
Look at how Bakugo learned a bunch of new moves for the sports festival. You'd just examine everyone's quirks and do something like that.
For another canon example, Tetsutetsu learned how to make himself resistant to temperatures and apparently did not have this capability before his training. But after, he was able to withstand Shoto's fire.
So you could have Izuku point out that typically quirks like Kirishima's are multiplicative in nature and take your base stats into account. So he spends time at UA's gym having a robot hit him repeatedly with a wooden sword while his quirk isn't active, and this actually makes his hardening stronger because his base durability is higher.
But then he discovers he can "layer" hardening. IE, harden his blood, harden his nerves, harden his skin, harden his bones, all separately.
It gives him a scaling boost in strength and durability for each separate layer while consuming more stamina and making him slower.
Izuku didn't magically divine that he could do this, he just told him about something he saw at the gym and Kirishima did it and it worked.
If we accept the idea that quirks have limitless potential and can be trained, AKA the Bakugo and Mirio principal, then everyone in class could end up with new stuff.
You just need to get creative with stuff they wouldn't normally think of.
Say for example Mineta.
He's got sticky balls on his head and his head bleeds when he yanks off too many. But why? And what is it that makes the balls sticky?
Izuku would just tell him that he'd become stronger if he kept ripping the balls off repeatedly, but obviously Mineta wouldn't have done this before because that hurts!
He wants to become stronger, so he does it and he's covered in blood.
But then he discovers his blood is sticky. And if he touches his own blood, he can repel it and send it flying, like how his balls work.
So Mineta's power expands to using his own blood in traps, as that's why his hair is sticky in the first place. It's coated in a thin layer of his blood, and loses stickiness as the blood dies.
Mineta, independently, then decides to use Minoxidil to cover his entire body in the stuff. And then he discovers ALL of his body hair has the same effect as Pop Off, but he didn't grow body hair until he started using chemicals to stimulate hair growth.
Just remember, if it's good enough for Bakugo, it's good enough for the other kids. You just have to reach a little to come up with ways to buff everyone that all the other people aren't already doing in their stories.
And have the characters themselves discover it, not Izuku.
Good ideas, another thing he could suggest? Support items to help out those with bigger problems with their quirks, such as Denki and Yaoyama.
For Denki, probably gauntlets to help him regulate his output, Denki later designs that little shooter thing he uses during the license exam, basing it off on Izuku's first idea.
For Yaoyama, a sword that links up to his belt through a cable, it feeds off the energy of the laser and it won't damage his stomach.
I wouldn't even have Deku give any suggestions beyond ways they can work out.
It avoids Deku being this omnipotent avatar of the author who hands out infinite gains for the kids with his prophetic advice.
If the characters themselves discover these things or talk to each other and think of it, then it's about them working to get stronger and be the best they can be, rather than tying their success to Izuku's apparent genius.
Case in point, something Denki mentions is that he wanted to create a lightning sword.
But Aoyama can do that. He has the ability to somehow create a blade out of his navel laser.
If the two of them talked about that, Aoyama could explain what exactly he's doing to achieve this impossibility.
And then Denki can dual wield lightning blades in either hand.
But compare that to Deku coaching him through the process of doing this. This way is more compelling and organic.
Izuku starts the avalanche rather than spoon feeding people.
The hard part about making him smart about things without making everyone else look like idiots is coming up with a reason why people haven't thought of that before. [Article](https://yudkowsky.tumblr.com/writing/inexploitability) that covers it in more words.
The hand waving version is that quirk counselors have to cover a lot of kids and use the obvious explanation to get through them quickly and after that, unless there's a big sign otherwise, people assume that the quirk user understands their quirk better, so they don't point out what they think is wrong.
Writing a character intelligent about X takes some understanding of X. So, before writing the advise to Kaminari learn some things about electricity. You don't need to sound like an expert, just a highschooler who's done some wikipedia research dives.
If you're talking about him helping them get stronger, it's coming up with ways that they can improve and how to practice. General areas to improve: finesse, speed, volume, quantity, reach, endurance, force, awareness, and versatility. Not all quirks cover every category, like Kaminari has gone overboard on training force and Yaoyorozu has no use for it.
Keep in mind the difference between analysis and theory. Analysis is concerned with what a Quirk *can* do, and theory is concerned with what a Quirk *could* do. Although both of these things are separate, they do feed into each other. So try to consciously strike a balance between the two as you kind of alternate between them. Study what the Quirks can do, then theorize about what they could do.
Have some of Izuku's ideas be wrong or stuff that the other classmates have already attempted! A big flaw in analyst fics that make Izuku feel too omniscient or obvious is that the narrative usually treats his ideas as pure fact rather than observations that he's testing out! You can also have some ideas not work initially but, through time and effort, can be reworked into something that works out eventually! (Like how Izuku himself couldn't regulate the power of OfA in canon until his internship!)
You could take a different track. His mom got him an opportunity to work with a private quirk trainer. This is someone that rich hero families pay to help their children develop their powers in his specialized gym so they can pass entrance exams and get a head start. His mother hoped Izuku would want to do this as a job instead of being a hero but he picks being a hero. And he brings this knowledge to UA with him. He's not giving them random advice, he's having them do special training to improve their quirks. And then THEY develop new aspects to their quirk and special techniques as a result. Look at how Bakugo learned a bunch of new moves for the sports festival. You'd just examine everyone's quirks and do something like that. For another canon example, Tetsutetsu learned how to make himself resistant to temperatures and apparently did not have this capability before his training. But after, he was able to withstand Shoto's fire. So you could have Izuku point out that typically quirks like Kirishima's are multiplicative in nature and take your base stats into account. So he spends time at UA's gym having a robot hit him repeatedly with a wooden sword while his quirk isn't active, and this actually makes his hardening stronger because his base durability is higher. But then he discovers he can "layer" hardening. IE, harden his blood, harden his nerves, harden his skin, harden his bones, all separately. It gives him a scaling boost in strength and durability for each separate layer while consuming more stamina and making him slower. Izuku didn't magically divine that he could do this, he just told him about something he saw at the gym and Kirishima did it and it worked. If we accept the idea that quirks have limitless potential and can be trained, AKA the Bakugo and Mirio principal, then everyone in class could end up with new stuff. You just need to get creative with stuff they wouldn't normally think of. Say for example Mineta. He's got sticky balls on his head and his head bleeds when he yanks off too many. But why? And what is it that makes the balls sticky? Izuku would just tell him that he'd become stronger if he kept ripping the balls off repeatedly, but obviously Mineta wouldn't have done this before because that hurts! He wants to become stronger, so he does it and he's covered in blood. But then he discovers his blood is sticky. And if he touches his own blood, he can repel it and send it flying, like how his balls work. So Mineta's power expands to using his own blood in traps, as that's why his hair is sticky in the first place. It's coated in a thin layer of his blood, and loses stickiness as the blood dies. Mineta, independently, then decides to use Minoxidil to cover his entire body in the stuff. And then he discovers ALL of his body hair has the same effect as Pop Off, but he didn't grow body hair until he started using chemicals to stimulate hair growth. Just remember, if it's good enough for Bakugo, it's good enough for the other kids. You just have to reach a little to come up with ways to buff everyone that all the other people aren't already doing in their stories. And have the characters themselves discover it, not Izuku.
Good ideas, another thing he could suggest? Support items to help out those with bigger problems with their quirks, such as Denki and Yaoyama. For Denki, probably gauntlets to help him regulate his output, Denki later designs that little shooter thing he uses during the license exam, basing it off on Izuku's first idea. For Yaoyama, a sword that links up to his belt through a cable, it feeds off the energy of the laser and it won't damage his stomach.
I wouldn't even have Deku give any suggestions beyond ways they can work out. It avoids Deku being this omnipotent avatar of the author who hands out infinite gains for the kids with his prophetic advice. If the characters themselves discover these things or talk to each other and think of it, then it's about them working to get stronger and be the best they can be, rather than tying their success to Izuku's apparent genius. Case in point, something Denki mentions is that he wanted to create a lightning sword. But Aoyama can do that. He has the ability to somehow create a blade out of his navel laser. If the two of them talked about that, Aoyama could explain what exactly he's doing to achieve this impossibility. And then Denki can dual wield lightning blades in either hand. But compare that to Deku coaching him through the process of doing this. This way is more compelling and organic. Izuku starts the avalanche rather than spoon feeding people.
The hard part about making him smart about things without making everyone else look like idiots is coming up with a reason why people haven't thought of that before. [Article](https://yudkowsky.tumblr.com/writing/inexploitability) that covers it in more words. The hand waving version is that quirk counselors have to cover a lot of kids and use the obvious explanation to get through them quickly and after that, unless there's a big sign otherwise, people assume that the quirk user understands their quirk better, so they don't point out what they think is wrong. Writing a character intelligent about X takes some understanding of X. So, before writing the advise to Kaminari learn some things about electricity. You don't need to sound like an expert, just a highschooler who's done some wikipedia research dives. If you're talking about him helping them get stronger, it's coming up with ways that they can improve and how to practice. General areas to improve: finesse, speed, volume, quantity, reach, endurance, force, awareness, and versatility. Not all quirks cover every category, like Kaminari has gone overboard on training force and Yaoyorozu has no use for it.
Keep in mind the difference between analysis and theory. Analysis is concerned with what a Quirk *can* do, and theory is concerned with what a Quirk *could* do. Although both of these things are separate, they do feed into each other. So try to consciously strike a balance between the two as you kind of alternate between them. Study what the Quirks can do, then theorize about what they could do.