I know this is an old post, but how would you be opening your entire network if you used the server as a VPN router? My understanding is that VPN is very secure. Also if you had a NIC, could you connect that to a stand alone router for VPN access?
He is opening his entire network to the internet. All the VPN does is provide a Secure Tunnel from his network to a remote user. It is does not in any way protect his server/entwork from the internet.
In these situation it is far more economical and reliable to user a hardware firewall that provides VPN instead of using a 2K server to provide the VPN.