I have to ask why can't you monitor their internet access through SME, if you can do it for local users, it would be exactly the same for VPN users as in theory they are just an extension of the physical network.
The problem is i don't have any option to monitor local users, "local users" are just some dedicated servers running behind sme.. the "outside users" i can't monitor, squid gives me empty logs and even if it showed me what those users accesed i am unable to monitor them in real time.
I just wanted a on/off switch, not globally, but per user.