New Brevoort Formspring

What happens if I brainstorm A REALLY GOOD idea about how to make Spider-Gwen possible in the MCU? I know that fans AREN'T allowed to pitch ideas, but is there a form of contract that I could sign where I give my idea for free so Marvel can do what they want with it? I think I have a great skeleton of a story stuck in my mind here and I'd really like to just give away for Marvel, instead of posting at a random forum on the internet. Is there any thing I can do? twitter: @taliontheundead