I'm not particularly aquainted with the abilities of CTF, but would it be possible to have a 3-team CTF game, only two flags (each playing team's flags) were out-of-reach, and the third was located in the center, but that team could have no players?
best way is to do neutral bomb, set it up so you have to bring the bomb back to your base, and put shield doors around the bomb and make it instant arm, instant blow up, and the shield doors will protect you.
There IS neutral flag, but I'll get teh banban if I give you the link. It's 1 flag for 2 teams, AND with Carbine and Plasma Rifle spawns, aswell. But, it's modded, so I cannot show you.
I'd never thought of using shield doors to contain the bomb's explosion, nice touch, should make it a much more robust gametype. Though there is one problem with neutral CTF as a gametype, or Capture the Bomb as it would be in this case, I'm guessing it's the reason for it not being included as a possible variant. 2 sided objective games like this rely on end to end action, players must traverse the whole length of the map at least once to score an objective. In CTF, you have to get from your end of the map to the enemy base and back again with the flag. In Assault and Neutral Assault you only have to get from your end of the map to the enemy base, getting back isn't a necessity, but you still have to traverse the whole map, you have to control the enemy side of the map if you want to score. But in Neutral CTF, or whatever you would call this gametype, you only have to control your half of the map to run objective. Keep control of your side of the map, with general control over, and strategic pushes on to, top middle. With this you can just get score after score, without even having to cross top middle. In fact, once you get the bomb off top middle and back to your side, you've got a seriously easy road to a cap unless most of the opposing team is in a position to stop you. Spawn conventions would dictate having team spawns focused around their own base, making this problem worse by meaning that players respawn at their own base, in a position to help team mates who are running the bomb home if they have it, but in no position to stop an opposing bomb runner if their team does not have the bomb. You could try experimenting with neutral spawns in each side of the map, possibly utilising respawn areas, to try and get some spawning on the enemy side of the map and help stop caps, but this is very dangerous in a healthy spawn system, and it would probably just result in FFA style respawns, screwing up the team game entirely. I liked the idea too just for the novelty of doing it, but the more I thought about it the more I realised why it's not a gametype.
Wasn't Neutral CTF a gametype until they took it out because it was broken? If I were you I would take Dimmest's idea. @ Pegasi - I don't understand why it wouldn't work well. It was good in Halo 2. Also, there is no way to have more than 2 teams on either bomb or ctf.