I joined the Steam comp group you made.
I'm not a high-end comp player. The most experience I have is being the Spy in my gaming group's highlander games against other groups, no prizes and such involved and more for fun. Otherwise I've done tf2lobby games and such, but honestly I'm not the best at comp gameplay.
This being said, I would definitely be interested in comp brink, especially considering I'm starting to grow more interested in comp gameplay. But I'd definitely desire that teams not be limited too extremely. In 6v6 TF2 the restrictions they have really make sense in the long run and have kept it interesting, but considering how Brink will work in comparison, limiting body types too heavily would just make it boring in the end. Only 1 heavy on even a 5v5 team would, like stated earlier, leave teams with only 3 options. With the addition of a second heavy, there would be more possibilities and thus more interesting gameplay which requires more coordination.
Like said by many others, though, I honestly think this topic(though interesting and I'm glad people are interested in such a thing) is a bit premature, as all the talk shows that people already think gameplay is going to be unbalanced. I think we need to wait 'til we actually play before we really even talk about weapon bans and the like.
That's what I think on the topic. Agree or disagree, I really think that comp brink would be really fun.