While an interesting concept, its limited very much by two things:
1 - in order to do this viably you'd need a very, very large pool of comps to pull from. In an MMO environment a good comp takes a while, meaning that this sort of gameplay isn't viable for many players.
2 - by banning certain pokes (either walls or wallbreakers) you'll make it very, very difficult for someone (especially someone limited by point one above) to compete effectively. While its true that you are also limited, 6v6 special sweepers only (to go by the earlier example) isn't going to be that interesting (especially because I suspect both players will have very similar lineups)