[@Rin]: You are in luck.  All three of those ideas are viable from what I have heard from the other players (as Sep has mentioned).

1) Spider-Woman: As Sep said, I am actually planning a clone saga like story arc for Spider-Man.  You can always PM me and we can work something out (I already have some ideas about how it could work).

2) She-Thor that is not really She-Thor: That is actually an interesting idea.  There is going to be a pre-established Avengers team and we can also fill in those spots.

3) F4: There are a couple people planning out the F4, too.  I think Gowi is intending to play as the Invisible Woman, Drewvonawesome as Mr. Fantastic, and Kid Lantern as the Human Torch, if I recall correctly.  I don't know whether you would want to play Ben Grimm, but the F4 is still an option.

All of those sound like good ideas and we would love to have you on board.  I think I remember showing interest in a game similar to this one a while ago that I was running.  Don't feel pressured, though.