I love the cosmic rays concept!...but I would want them to have totally different powers from their own and from the original FF. Has it ever been explained why the FF got their own specific powers...is it simply based on something in their DNA or personality that reacted to the cosmic rays? (Johnny Storms a hothead so he became the human-torch). If so you could have lots of fun coming up with original powers based on the Flight's DNA...personality and history.

I remember Walter was in college with Bruce Banner so it seems that he would still be condemned by fate to be the strong guy...but maybe not. Off topic a bit but I always like the idea of a supergroup all having the same powers but as time goes on they discover didn't ways to use them.