If there are weapons that are banned at the highest level of play then valve should definitely HIGHLIGHT those unlocks and have a talk with the best players in TF2 to get an understanding of why they are banned. Valve needs to also look at the unbanned weapons that aren't being used at the highest level of play.
If anything I think valve should make a balance mod for both HL & 6s if they have to and test all inferior or banned weapons repeatedly until they are deemed balanced.
I think 8v8 would also work better for their lobby system with 6s class limits as it resembles the player count vanilla TF2 originated as IIRC
It good to see that valve cares about competitive TF2 and are actually trying to balance out this game.