I'm trying to setup where a specific person's web traffic from outside of my network goes through my router and appears as if it was originating from my network. The only requirement is their traffic needs enter my router, be redirected back out and appear as if originated from within my network. Encryption is not necessary, and they don't need to be visible within the LAN itself. I would prefer it to be handled strictly within the router, but can setup a server within the network if necessary.
I'm assuming that can be done by setting up a proxy or VPN, but have no idea where to start.