Although this sounds interesting, except for the Main Character being a bit overpowered, it's also a massive undertaking. A lot of new writers greatly underestimate the amount of work a project takes, and either leads to very rushed games with only a few words per page, or these horrifying games that are released in parts, or demos, or previews or whatever the hell excuse the author picks, so take this into consideration when you're going with such a massive concept.
As for the actual inspiration, I've found it best just to write, and see what you come up with. Just start writing and see what you come up with. Try reading other storygames or just doing anything else when you hit Writer's Block, and never try forcing it, because it just makes it worse.