I like to get a bunch of pillagers and have them all break their crossbows so they basically become passive and be used as guards. BUT there are a lot of problems with this and makes it hard to do longterm

1. The illagers become stupid and eventually walk their way off cliffs
   ( I've lost 7 pillagers because they all walked off of a cliff without hesitation )
2. They don't seek beds at night
3. They make villagers panic, even though they have no weapons
4. They wonder around with no goal.
5. They can't open doors iirc
6. And they might be able to pick up weapons ( not sure about this though )

I think a good way fix this is by giving illagers without weapons the villager AI, this will allow them to do mostly everything a villager can do and add some variety to the population

Not sure how much of this is doable, but I will look into it.

The way witches and zombies are done is to delete the old mob and spawn a new mob. In this case, we'd want the illager to retain the illager texture and/or mesh, I assume, so that'll be the interesting part to see if it's possible.