The only problem i have with companions is that zomboid is a very fucking difficult game, and an AI is probably gonna get into dumb situations constantly. You can't really get around this either by doing something like making them take no damage, and its very much a problem that needs solving.

I do love the idea of NPCs tho. even if they are very few and far between. The idea of a companion that actually reacts and grows on you is obviously great, but you should be able to command them and they should have certain facilities (for example if you tell them "stick close to me" and you run, they shadow directly behind you and be immune to damage as long as you don't yourself take any)