Frick, I wanna do this! I actually can world-build at the snap of my fingers, and I've always wanted to make a game, despite not having the talent or patience for programming...
But...I gotta know what this is about. You say the party starts at around 5-10 characters and rises to 20-25? How on earth does that work?? I'm not very well-versed in RPGs, so I'd really need that explained to me. Do you switch through party members at save points or something? Or are you just carrying them all around with you like a weapons' store?? It just sounds like too much...
And secondly, what are your plans for this game? Are you more motivated by the idea of creating something or the idea of making a profit? (Either is fine with me, but the tone of the project kinda depends on it.) Thirdly, have you ever worked on a long-term project or a collaboration before, and if not, are you prepared for what that entails?
Fourthly, I'd be very willing to help with art and even assets if need be~. ^^