Route through another gateway

[TheMephistophelian]

I am wondering if it is possible to route traffic from a certain source (IP or SSID) through another gateway on my local network on a N66U running ASUSWRT Merlin?

Specifically, I have a server, 10.0.0.100, running a VPN tunnel, and I want to make select sources use this server as gateway instead of the N66U.

Say my Mac is on 10.0.0.50, if I pull DHCP from the N66U (10.0.0.1) i get:
IP: 10.0.0.50
Subnet: 255.255.255.0
Gateway: 10.0.0.1
and connect through the WAN.

If I manually adjust the gateway configuration to 10.0.0.100 on my Mac, I connect through the VPN.

I want to automatically route traffic from my Mac (10.0.0.50) through the VPN gateway. Is this possible? I have looked into routing through iptables, but so far have been unable to come up with something that works.

The solution would be somewhat similar to routing a specific SSID through the OpenVPN client in the firmware (or the new Policy based routing option), but instead of using the built in VPN client, I want to use my own.

Am I going down the wrong path, could this be accomplished in some other way?

Thanks!