I think an abusable portion of these 2 suggestions is who would have access to the character being held in thrall.

If someone {'accost' or 'autokill off'}s someone else, perhaps only they should have the ability to finish the kill, or attack that person. I can see an AP's group all stopping, and letting the AP get the final blow. I'm sure some of the best AP's out there would have been Alot more powerful if they were assured the kill every time.

So to sum up. I like, generally, both ideas (Autokill off better), but the abusable attributes would have to be flushed out quite extensively.

-Cassman-