Pillagers can wear banners (probably in their head slot)
Pillager Banners give Bad Omen (probably consumed on use)

Is this a suggestion?

Yep, guess I should've mentioned that

Pillagers don't start raids by themselves when they get in villages though 🤔

Currently, there is no way to start a raid in mob form as killing a pillager while possessing a mob doesn't give you bad omen. I'd say this could be an interesting way to make it possible to start a raid while possessing.

I like this idea. Also, villagers should be able to get bad omen.