Personally, I think we should be able to bring in our friends. As long as the core of the fleet is made up of Trek BBS members we should be fine.
I know I want to be able to play with my non BBS friends.
I am not sure of the exact method for leaving a fleet. I would assume there is a button on your fleet status screen. Try checking there.
Since there are five people here who are interested and at least a couple are interested in bringing friends I will go ahead and see what is required to create a fleet in game.
I will report back here when I have more info.