Lol, I'm working on a chrono game already, so once that's into it for a while, if the RMXP idea pans out, I can upload some pre-assembled maps.
I have Game maker as well... but I never got even as far as getting the two to connect... I'm willing to mess with that too, though I'm sure if you got that far, my moderate level of GML knowledge won't be of much use...
However, if you do get this working through GM, I'd love to see your code, as I have another online project of similar purpose...