I don't think stress makes Ariin live inside a werk... Or explain why his electronic eye is no longer fully under his control and seems to spew whatever Paladin's view on things would be in rather creative fashion. 

In other new's Paladin and Katya are conspiring to make Ariin a decent person. Also, Paladin has learned to speak through the screen in Ariin's ocular implant which basically where he lives. Whether you want to believe it's Paladin controlling it or someone else your call. However, it does have a mind of its own and Ariin cannot tell what it is doing only knowing that Paladin is messing with the screen. 

Paladin remains an asshole to his pilot. Why? Because a massive war machine is now trapped in a glorified glass eye, he's going to get bored without something to do.