...give him a coin as a parting gift then dispatch him to Oblivion. The bonus of this is apart from not having him saying he hasn't done anything you also get a letter of inheritance of 90 gold. Just encase anyone didn't know. Now why wouldn't you kill him?

I use him for the speechcraft boost to sell stuff for higher and persuade people though!

Becasue killing an innocent man isn't worth any amount of gold, especially only 90. An plus, he wouldn't go to Oblivion, he's not a daedra

Banish enchantment?