Having run a Munchkin table of 10 players, I can tell you that 8 is the absolute most I will ever allow, ever again. Adding the idea of multiple players playing at the same time is just going to make it way too confusing, and I honestly don't think this is going to work. I guess what I'm trying to say is, if you really like pandemonium and mayhem, why not just take a bunch of kindergarteners to play paintball?
But, some more thoughts to why this is a bad idea:
- What happens if one of the active turns laps another? If you don't allow turns to move until all the current active turns are completed, how do you combat bordedom of the player who has to wait for his turn to happen because he's ready to go (the previous player had a fast turn), and one of the other active turns is in the middle of an epic battle. You can't guarantee that everyone's going to be interested in a battle they can't influence (i've seen it happen in 3- and 4-player games, so don't tell me it's less likely in a 30-player game).
- How many cards are you thinking you're going to use? You'll use up cards very, very fast if you're going from a single deck, even if you blend in every possible set and spend a lot of time re-shuffling.