Maybe a bit of an unpopular opinion here, but as a player the worst part about sigafoo's earlier 7v7 tournament wasn't actually the gamemode, but rather the tournament organization. I remember at the time of the event, the biggest complaint most people had was that in order to play the tournament they basically had to be on call for like 7 hours straight b/c of the map/weapon pick-banning as well as the matches themselves. Once the games actually started they weren't that bad to be completely honest, and the most "gay" thing about them was learning to play with and against the specific skillsets of the players you had in the server (thanks spamfest n_n).
6v6 to me is the more competitive gamemode- but I don't see why people have to pretend like it is the only thing that can ever exist. I personally love playing non-6s tournaments when I have the chance, be it ultiduo, 4s, HL, or this stuff. Variety can be fun, and sigafoo can use his money however he wants. Also, fwiw if you have a stock 6s tournament you are literally feeding froyotech the money. New maps or alternative gamemodes give other teams better chances to upset them (dk gave froyo close matches in the last 7v7 tournament, and evl beat froyo in the new maps cup) so if anything I would think this kind of stuff would be welcomed in at least that aspect.