Marelli
Okay, if you want to make things more exciting when the battle is grossly mis-matched, how about his:
Attackers can chose to enter "fast mode", wherein the battle lasts an hour instead of 2 hours, if they chose to do this, the rounds are half as long and the guard spawning is thus twice as fast. If they chose to do this, it can't be undone anymore.
That would be a neat thing to try out.