You need to prove you can make something first. You can't just be an ideas guy and RPG Maker is no shortcut to being able to program (if you do not, it will feel completely generic).
You're asking people with time-intensive talent (art and music) to contribute while you do the fun parts of writing and designing, or worse "managing" a "studio". I've seen so many fangames fail because of this.
Don't waste any time coming up with names, characters or ideas. Get something running with placeholder graphics that shows what makes your game unique and only then try to get talent. Come up with a design document showing your plan, again with as little of the fluff as possible. Get familiar with the program you'll be using or better yet make your own.
I'm extremely not surprised that the first guy to volunteer wants to write and has 'always wanted' to create manga.
