OlghaI personaly watched "cat noises" a lot, as it is, in my opinion, the most interesting team to watch, not only because they bet Froyotech on upward week 2, but also because they're really into trying new things, which lacks like a LOT, as i already mentionned in my other threads about pyro/heavy where people would not easily be likely to play against something unique.
There is absolutely nothing stopping you from trying to establish something unique in traditional 6s. The only problem is that there is a high chance that it won't be viable but still annoying to play against. Also, there is only so much shit you can make available before a match of 6s turns into an unorganized, convoluted shitfest. I don't think you'd consider Overwatch a good game to watch, but that is pretty much what TF2 would be with all that no restriction stuff and I don't think we can afford to make 6s even more complicated if spectators that do not play it can't wrap their head around the whole Ubercharge business. Apart from that I'm pretty sure even in Overwatch they form a composition that is just inherently superior to any other.