The game is played in a map, where it is auto-gen'd. However ops can also change this and it would be very interesting (a treehouse in the middle of the map for sight!). Team bases are not in the corner, so people can sneak past it. The idea:
1 is team one's flag, 2 is 2, etc. 3 and 4: Make it a option for a 4 team game. Why not? Would be interesting.
Make the same as survival.
This will be VERY fun. You still have arrows and meele, and with crafting, you also can kill your enemies! Here is a idea: The map is divided into 2 (two teams) or 4 (four teams) areas - if you are within your team's area, you do double damage. Simple as that.
To capture, make a special 'flag' block. Take 10 seconds to mine, and you will be announced, eg Notch now have Team 3's Flag! You cannot damage while holding the flag. If you die, flag is where you died. Carry it back and build it within a 5x5 distance of your base, or another of your flag. If you have no flags, you have 2 minutes to get some flag or your team loses. Last to survive wins!
Ok, it is annoying. BUT! Only 2 will be spawned (2team) or 4 (4team). Spawn it every minute!