In the end we played mono colour decks without proc creatures, landwalk or hosers. I played blue making my allies white and black and my evil enemies read and green.
A little planning beforehand gave me a nice creature sweeper deck while my allies had regenerators and en-kors so they survived the damage whilst red and green did not!
Let me explain how I did it.
Floodgate 3U (Mirage)
0/5 Wall
If floodgate gains flying bury it
If floodgate is removed from play it deals 1 damage to each non-blue non-flying creature for every two islands you control.
Vodalian Illusionist 2U (Weatherlight)
2/2
UU, Tap: Target creature phases out.
Kind of archaic cards I know, but they gave me an eccellent reset button and some aditional control. (Whats that? Your flyer survived? I guess I'll have to phase it out every turn for ever!)
The rest of the deck had Capsise, Whispers, some counters (Counterspell, Forbid, Foil) and Seahunter.
I won once, red one once with some kind of Kyren Negotiations deck (Actually quite good in multiplayer - stop laughing!). And black picked up the rest of the wins by sitting around behind fogs of gnats and skeletons doing nothing then going Corrupt, Corrupt, Soul Feast, Soul Feast win etc..
Much fun was had by all and I suggest it to everyone. Next week we play two colour decks with the colour hoser restriction dropped. I'm going to be playing green white. Perhaps I'll bring out my old Thicket Basilisk/Lure/Jangling Automoton deck. With Armadillo Cloaks! Isn't multiplayer great!