I read this thread and started daydreaming a bit.
Regarding level scaling I can think of a system based on dice rolls. The system could make a roll for example with d4 or d6 for all enemies, result-1 or -2 to be added to the PC actual level = enemy level. After that adding skills and abilities from a preset pool for them. So there would be differences in a group depending on 'luck' and a combat can be different by playing it again (loading older savegame). The game difficulty level could give a modifier to this roll.
I simply wouldn't show the level of the foes until the battle starts (or never for maniacs, hehe), so it could be also fun as player not to know how strong exactly the enemy is. This could avoid to get bored (but maybe also go on the nerves after some time, hehe).
However there are huge problems with this, this can unbalance the game quickly, devs have work a lot to be able to handle this right and the KI has to be very good to be able to handle such a random group most effectively.
Dream off: I don't think this would be implemented in a game, since this may be too much work for a not too big feature...
