Have you guys completely forgotten about Morrowind? It's called 'dispose of corpse'. With the help of Havoc though, it would more than likely be possible, even if it wasn't actually intended for quests.
Emil did say in an interview though, something to the effect of "Thief was all about hiding bodies and bashing people over the head. You probably won't see things like that in Oblivion, but blah blah blah.."