Thinking more on Ironman; I think a Warrior would be too easy while a Paladin may be difficult on either hard or impossible at the start, once you get Res 3 however, it would become quite easy. Maybe a Mage on hard would be a sufficient challenge. I'd like to see if it could be done on impossible though!
Perhaps a mod could be done so that you can't exit a battle once it's started and the game itself will only save on exit from the adventure map?