This is a pretty good idea. But I assure you it isn't that easy. You will defiantely need a cp feature that reads what forums you have them you have to put next to them how many post counts a user has and if they can see them. That would be the easy part. The hard part would be displaying the forums depending on post count. I would try and help but I don't think I would get anywhere. Maybe some one will look into this when 6.1 comes around, this upcoming week.