That armor-changing trick will only work on Klint because it uses a different proto file when you remove his armor. Not the same with any other party NPC. Although I do not remember experiencing such a bug in the game, I do remember seeing this bug (NPC apathy bug) fixed in one of the later versions of Killap's fixes (and, by 'later', I mean one of the fixes that has yet to be included because it was after his January patch release and after I went away for real life issues). It is a bug from the 'vanilla' game.
I have no idea how he might be reset mid-game.
I have no idea how he might be reset mid-game.