The problem is that when people could switch to the dominate teams banner, is that it helped even out the pub stomping. If only clan people can rock a certain banner, they will be even MORE dominant in public servers. So it makes the problem of pub stomping even worse than before...
I totally like and want to be playing with my faction mates...however, it's a public server, and team balance is more important than banner balance. I still think teams could be balanced with factions almost 100% being on the same team, but it would take some re-working of the balance algorithm.