Understandably the game wouldn't be able to run off of Assault, but I think it could possibly work with other gametypes. Would you be able to do a similar set up using Oddball? Can you still get markers to bring the Oddball to to score points? If so then it'd definitely work, you could make the map a great big circle (or 16 sided shape) and have everyone spawn at the edges. I'm really stoked for this, if we can get it to work then it'll be boss!
You can easily do this with stockpile. I already made a game called FFA Flag, which has players fighting over a single flag to take to thier base. Just tweak the settings and voila! No epic splosions though Also, the game is team based, just with one person per team. The team limit on stockpile is about 6-ish? So you could only have 6 players playing at a time. Dont know if theres another way to do it