A question came up in a game with my kids on the weekend. My son was the Overlord and had Brilliant Commander in play. When revealing a new room he wanted to upgrade one of the demons in the final room to boss, but there was already a boss demon. Is he allowed to do this anyway since there is no boss demon model available? I know he couldn't if he was spawning new monsters.
(This was further complicated by the fact that it was the scenario where the final room has three demons - one boss, two minions - and you are supposed to us a minion giant model as one of the demons. To which my son cleverly declared, well then there is a boss version - the red giant - to upgrade it to.)
Fang