Hahah, true! It is quite painful to realize in Disciples that you are facing far more superior force, which you just don't seem to be able to win and to face the fact that... you just saved your game and the next save would be from the start of the scenario.
Bye bye my most powerful leader.
Back to the subject... I don't think it would work very well in this type of games. In King's Bounty you have large numbers of creatures in stacks. How would the leader be then? Mage/Warrior/Paladin 1. What would he's stats be? How he could go against hordes of dragons? In my opinion, it didn't really work out so good in HoMM IV and it would not work out very well in KB. If anyone has an idea, how to actually get the leader to involve in to the battle and make it work well, I'm all ears.