Personally, I'd say the party needs an archer. I'm surprised that I haven't seen any longbow-related twinking, really. If anyone wants to play an archer, go ahead. TWF is fine, too, though I have my reservations about the effectiveness of that path compared to the brute-force two-hander.
As a party, don't go overboard with the fighter builds. It'll be useful sometimes, but usually magic is the order of the day.
I've thought about it, and expanding the party to six people isn't a problem. I'll just throw more monsters at you. So lord_raven and bloodweaver can play, if they like.
Incidentally, I won't be able to post again until Thursday. Got stuff that needs doing...
Whatever you do, try to have your chars ready soon. I'd like to get started.