Competitive iT (or some other name that fits the description):
This Server would be 24 slot. It would run maps from competitive leagues in the rotation (UGC and/or ESEA), with the settings from that league as well (no crits/weapon spread and item bans). Classes would be reduced similar to that in ESEA 6v6, but modified for 12v12. Any class allowed 2 of in 6s (Soldier, Scout, Pyro, Sniper, Spy) would be limited to 3 per team, and any class that is allowed 1 in 6s (Medic, Engineer, Demoman, Heavy) would be limited to 2. Players could vote for maps, based on a list taken from a specified league (or both). Would NOT run any competitive config though (teams would NOT have to Ready up).
OR
Highlander iT:
18 Man server, 9v9. Highlander settings with UGC Highlander weapon list + map list, as well as similar settings (no crits/weapon spread). No highlander config.