We should keep the body as an AC in case we want to try interrogating his spirit.
That's the plan -- only Thera wants to go one step further and have a magi bind the spirit to his skull and keep him permanently.
Alexei might have some personal issue with that as it's pretty far from what a Christian would do. However that shouldn't stop Thera from doing it.
Isen is all from having an AC. Othervise, he doesn't care, save that, once everything is done and we don't need to interogate him (maybe years later), the man should get a proper burial IF he is not judged worthy of such punishment.