Reputation Affects Permissions
 

Is there not already something that will alter some aspect of a member based on their reputation? Something like: reputation falls below X and new post permissions are lost, etc.

There really isn't anything that does this already?

It's been in vBulletin for a while. I used to do it before the Infraction System was put in place. You can setup "promotions" so that when a person hits X reputation they are put in a different usergroup and you can set that usergroup to have less permissions.