Mafiascum.net

But I don't want to be the mod. Can I submit an idea to everyone and just let anyone who wants to run it do so, and if yes, how do I do this?

if it's an open setup, you can make a thread for it in the Open Setup Discussion subforum; otherwise, I'd suggest putting it in the Theme Test Market thread in Mafia Discussion and indicate that it's not something you're interested in running but hope someone else does.

It's semi open. The setup relies on a certain mechanic.

I think it should go in the Open Discussion topic.