Ok, so I'm not sure really how this would work, but I had this idea, what if four people dueled each other, 2v2? It would use a die to decide the play order, or a coin for the side that goes first, and then another coin. The field of play for permanents and creatures would be expanded, as well as maybe giving both players a weapon&shield slot. Health may or may not be combined, to avoid targeting confusion. The allies can see each other's hands and chat in private.
I'm not sure about many details other than stated here, so...yeah.