Well, it seems I took the Game Master duty so I am asking you some questions before I set the ooc and the game threads. I am going to ask some questions just to help us set a common ground.
1) Do you see this roleplay taking some extreme sexual direction, like rape, extreme bondage or something like that?
2) Does the mutants and radiation mutations are the single source of powers over the world or not?
3) Do you would like add non mutants elements at the gaming universe, like spiderman or avengers elements?
4) Do you would enjoy it as a part of soap opera and a part of action or more action and intrigue oriented
1) I think that is really up to what the players and GM want. I'm okay with NC, bondage, etc. I'm also quite content if this game remains "vanilla" in the sex department. However, even if there isn't a whole lot of interest in NC or what have you, if there's enough, it is my suggestion that the game be put in that category just to please those people when it does come around no matter the frequency.
2) I think it's best to keep it simple here. With each new origin we allow it creates for that much more complexity in which things can get convoluted and messy. On the other hand, complexity isn't necessarily a bad thing. I think, ultimately, it should be the GM's decision.
3) The decision for this question should go hand-in-hand with the decision for question #2. I thought at one point Marvel had decided that all metahumans were mutants or that all mutants were meta-humans, I forget. Either way, it's easy enough to claim that spider-man is a mutant or that the Super Soldier Serum made Captain America a mutant.
4) I'm easy here. I enjoy the action, but it is my experience that too much action makes it difficult to develop characters and explore intracharacter relationships. On the other hand, moving from mission to mission with little downtime allows for the game to remain constantly active and decreases the chance of people growing bored with it.
Some tough decisions, and I'm not sure I helped any, but hopefully the others will give you more definite answers.