The allure has always been tempting haha! I've dabbled with customising WordPress Forum Plugins in the past and making something that way, but an entirely new forum script is a huge undertaking. Would be nice potentially though!
What new would you offer? Many forums and plugins offer similar stuff like image add, rewards, contest. I don't know what new can be added on forum and it is not already done. Maybe something for stoping posting to similar posts? I am not to familiar does something like that exist.