Okay, so regarding difficulties:
The main advantage of forcing everyone to play Lunatic is that the matches will all be standardized, so in a sense the rankings feel more legitimate.
On the other hand, I want to make this tournament friendly to people of all skill levels, not just PoFV specializers, and I'm worried that on Lunatic difficulty, new players will be dying more to the game than to each other.
Well, on the other other hand, if you are new and can't chain well, you probably won't be sending much to your opponent's side, so, it might be fine to leave it on Lunatic only.
Your input would be appreciated!