Wow where has this thread been all my life? I’ve been brainstorming some similar forum gameplay for a bit now. You should check out my game thread:
Trinity Bash! (A Very Basic RPG)
As the title suggests it’s very simple, but it hits on some of these elements. I can already tell you that the more simple the better. I really wish the threads had more tools to aid with gameplay but you pretty much have to rely on the players to understand and self-enforce the rules (and do the math)
And however you keep score or make shared information available to the players is a challenge. You can post a wiki somewhere in the thread for this (I suggest the first few posts), but as the game progresses those posts will be further down the chain and harder to find.
As someone previously said, a game like this would work best with a small and dedicated group. I don’t think there’s a huge appetite for highly complex games–I could be wrong–but I myself would love to participate and hear more about the system you’ve developed.