I hope the quick fix doesn't get banned next season. It sure isn't fun for anyone when a heavy and a QF medic roll out but it is really good seeing the game shaken up a bit and some discussion happening.
There are a few changes Valve could make to the quick fix that would make it more friendly to 6s. They could remove the heal rate from the medic during charge so they are as vulnerable as when using a kritz. They could remove the no airblast effect so that pyro has a place on the team during static fights. They could even make it work like uber so that points can't be capped while under QF effect. Realistically though Valve won't change it, or at least not for quite a while.
I think the answer to the quick fix is more unlocks. Give teams more weapons to use, give them more creative items like the conch, give players new ways to think about the game so that they can adapt. I shudder to think about more guaranteed crits in 6v6 and I hope we can avoid that but the reality is the meta before the QF was really stale.
The 6v6 community has set up a box within TF2 to try to exclude all the boring and frustrating parts of the game. Running around a corner into a heavy is just as boring as getting headshot from across the map though - congrats you picked the right class and clicked. As long as this box is set up within TF2 I would like to see more classes played and more weapons used competitively. Lets see what crazy strats and wacky plays come out of the QF and anything else that gets picked up in 6s. Just leave the crit weapons out, Highlander would be way more fun without the RNG kills. With so few new maps coming into competitive TF2 something needs to be added to make it more dynamic.