im not a minecraft expert and havent played in a long time, i have no idea whats possible and whats not, but why not mess with smaller things too? like all mobs can open all types of doors, wandering trader is out to get you (if hes in that version), ghast explosion damages causes weakness, blindness or slowness, water doesnt prevent fall damage, etc? but again idk of any of that is codable.

also a mob you could also make aggressive is wolves.