There was a version of Star magic printed in the Duelist (Issue 4 I think, I'm researching to be sure and to find the exact rules as they were printed in the magazine). One of the best features I remember from those rules, that I think would lend itself well to casual EDH, was blocking "en passant." (1)
The idea was that if the player sitting in the W position wants to attack B, his creatures must move through U's territory to do so. So U had the ability to block first, any creatures not blocked went through to B, who then chose blockers. Combat step was then finished simultaneously.
Where this got intersting in the games I remember, was that since W and B are both U allies, politically he has a hard choice to block (help B, make W mad) or not block (Help W, make B mad).
Also, IIRC, the winner was the person to kill both enemies (not just have 2 enemies dead). For example. B and G are dead. If W kills R - W wins (though U would also have 2 dead enemy colors). Lastly (I can't recall if this was a house rule when I played in Detroit, or if it was printed in the Duelist as well) when we played, if (using my earlier example) R killed himself or died to drawing an empty library or in any way wasn't killed by W or U, then the former allies turned on each other for the final win. Ignoring all of this shortens games and we rarely played it out.
I imagine this would work in EDH with true star (monocolored, sitting the correct positions) Allied Colors, Enemy colors, Shards, Wedges or just any five decks sitting random/assigned locations.
Mostly I just think the "En Passant" rule would make a lively addition to the political nature of EDH.
V/R
HK
1: En Passant is a chess move that was borrowed for the rules printed in the Duelist. Learn more about it here:
http://en.wikipedia.org/wiki/En_passant