Thank you for the interest and the great advice :)
I'll try to answer all questions:
Tone: I am not interested in a comical game, nor in a dark grim dark one. I'd say something along the line of heroic with a streak of dark in it.
Rating - at first I wanted this to be an Adult game, I like the freedom it give to explore interesting story lines but after much consideration I figured I can get as much from a Mature game.
System - Marvel had introduced a power grid for their characters, it is a 7 step (2 normal human) on different aspects. The Marvel database
* also give a good soft description of powers and talents. I believe this should be enough of a system to give people the scope of their powers and abilities.
Conflict - I important a very basic dice less system to measure conflict. Each hero divide 100% focus between Offense, Defense, Maneuver and Others. The higher side wins, I'll give more details should this game fly.
Growth - My intention is for each player to suggest a character and a What If moment, with suggestions on how this change would impact on the world. Once the player is approve will run the What If to the point the hero is recruited by the Watcher. I think personal growth, personal goals and interests should be the drive of the game.
Please let me know if I missed something :)
* see link: https://marvel.fandom.com/wiki/Marvel_Database