It won't be tweaked. This is the format this type of event will be in. Yes, it means you can't use mono decks. You must either use a duo or trio. With three elements to choose from in each match, there are many, many different decks you can build in each one. The point of this event is to test your ability as a deck builder.
Edit: Slightly ninja'd, but you're getting it from the horses mouth anyway.
Edit2: One rule I would be willing to change: should decks be changeable during matches? I made it so you couldn't just so match reports would be simpler, but I'm thinking about letting yall change decks mid-match to emphasize deck building.