Now the switch could filter by port by only alloing one mac address to associate.
could you please explain how this can be achieved? may be i'm not getting it right but did you mean there is away to do MAC ACL on a switch?
And yes, a small router at the client side would fix things.
I already have that implemented in most of my clients, its working to some extend but there are clients who knows how to beat it so they just plug out the cable from the router and plug it to a switch.
I'm already subscribed to SmallWall forums and I've been following the posts there closely, I'm really hoping it will come through, I like the concept to maintain a lean firewall.