Using a PFsense with multiple nics you could set up numerous networks and control routing between the networks at that point. Also pfsense can fully intergrate openvpn into the Scheme and has a firewall and filtering to be able to tell where everyone in the network is going. It also allows for port forwarding for you Linux box. did I mention all of this is done through a GUI interface. Software can be downloaded at: https://www.pfsense.org/

I have ran with the version Ubuntu not a huge fan, lots of nice features although not really what i was looking for. If you are looking for something easy to use i prefer to use Linux Peppermint. Really nice OS, still in development, although installed it for my 5 year old and he can function with the OS very well, and it just works. I installed it in an old HP desktop with Old P4 running 1 gb of ram and the system perfoms well with the peppermint.