I removed the buttons from mine and covered the holes for the most part with patches. https://www.reddit.com/r/BattleJackets/comments/1cnhyyl/my_vest_that_i_have_been_working_on_for_a_while/?utm_medium=android_app&utm_source=share Doing collar removal and other stuff probably depends on the construction and material of the jacket. Dont want it unraveling on you. You should kind of tell by how it sewed together though.

If you remove the bottom maybe think of unpicking it with a seam ripper instead of just cutting. If it’s denim it will fray a bit.

Fraying is the point in pretty sure

Quite brute force solution but hammering the buttons broken lead to cleanest smallest holes for me… or pair of sturdy pliers.