CTF duel tournament is...unoriginal to say the least. A battle tournament would be boring. 2on2 TB sounds nice, though 2on2 tournaments have never been successful in the past for some reason. Clan TB with 4on4 sounds plausable as clan tourneys work, though it would be better off as 3vs3 unless you want even more forfiet losses due to unsufficent numbers of people showing up. 4on4 assault sounds fun, but it's best to keep it simple as players and clans will complain how they aren't the best at the gametype and how it doesn't allow them to have some of their other skills 'shine'. TB is the most simple gametype that anyone can play that will allow the most diverse playing styles.