that's the easy bit, no?
it can be borrowed from the various MODs allowing various things based on post count, points, cash, what not.
even if that wasn't borrowed it's the payment gateway stuff that's the thing that kept most people from writing a MOD like this, the ACP part you can even review the phpBB code for forum permissions and work from there.
Reality is that which, when you stop believing in it, doesn't go away
- Philip K. Dick
Reality is that which, when taken away, you can stop believing in
- Aysla Crystal McGregor