When a Wither Sickness infected mob too long. He becomes сompletely withered

This is already implemented in the form of the sickened mobs (currently only the zombie, creeper, skeleton and spider), unless if you're thinking of something else.

This is already implemented in the form of the sickened mobs (currently only the zombie, creeper, skeleton and spider), unless if you're thinking of something else.

one thing you could do is make it so when it is fully withered it becomes entirely frozen (just remove the A. I.), then it gets pulled into the wither storm, with particles like when the player is pulled towards it during the re-awakening after the formidibomb knocks it down. then, the mob appears in the bowels of the witherstorm it got pulled into. (you could even make them reappear and have hostile a. i. instead of making an entirely new mob.