Or if new members received an automatic welcome message saying hello etc. and then a brief summary of general forum rules? Since there's no real reason to visit this thread.
Maybe when you have create an account instead of redirecting you to the forums. Maybe have 2 buttons at the bottom of the page saying 'Proceed to the welcome wagon' and another button saying 'Appeal your ban' Don't force them to make a welcome wagon, just kick them in the right direction. It would make people stay longer if they make a wagon post and get good, friendly replies they would be more inclined to stay. But downsides would be more welcome wagon posts. It may get a bit stale