Although this is exciting, there are so few players where I live currently, I'm hoping we can get enough to even try it out.
From what I understand, it doesn't seem overly complicated, its trick will be found within the gameplay itself (which is how I've always believe multiplay ccg games should be).
New terms that come into play and become critical are Rival, Adjacent, "Your Opponent" and "An Opponent".
Basically, your opponent to your left is your Rival. You will always play before your Rival.
Your Rival's Problem deck is considered Adjacent.
You may only play or move cards onto your own problem or that of your Rival's.
(Thus you can still only play Troublemakers on either your own problem or your Rival's. However, the player to your right could play a Troublemaker onto your problem).
You may only move cards controlled by other players to either problems of their own or their Rival's.
Other exceptions/interpretations: When a card refers to "your opponent" or "an opponent" you must choose any one opponent. Only when a card specifically refers to "each player" does it refer to all players.
It becomes more complex and interesting past 3 players. (Remember, you will only be directly dealing with your problem deck and your Rival's problem deck).
However, the one beta rule I'm not too convinced of - specifically when coming to playing Resources or Events - is whether these should be restricted to playing only on your own problem or that of your Rival's. I think the ability to play Events, and especially Resources, beyond this limitation could make for some interesting strategies. (Helping establish alliances, at least temporarily!)