See the problem with that is the fact that they are going to be in town a lot. Evil is once thing but a re-animator is quite another. The cleric of the party is going to be one of the undead smiting ones. So...a re-animator who turns into a lich isn't party dynamic...it's suicide.

If you have read the comics then you know that Roy gets in trouble when he dies for allowing belkar to do the things he did. Even traveling with him got him in trouble.