I was just wondering if anyone would be game to attempt this. For those who have played Redguard, you'd know that trolls in that game would collapse once beaten, regenerate after a short period, and then spring back to life. The only way to defeat these seemingly immortal creatures would be to torch the corpse. This mechanic carried over to Oblivion in a rather uninteresting way - a slow automatic health regen and a weakness to fire.
Something like this would probably require OBSE, but I thought that I'd put the idea out there. Its wanted.
As a side note, this might be much more easily accomplished in Skyrim, which already has a 'recovery state' for most enemies, including the troll.