Sharing two sources of internet with one cable possible?

I have two internet sources, one is at one end of a Cat5 cable, and the other is at the other end.
Basically
Location A (NET1 (Tomato router 1))-------------------------------- Location B (NET2 (Tomato router 2))

I want to be able to use NET1 at location B, and NET2 at Location A.. Basically somehow build a bridge between the WAN port of Router 1 and any of the ports in Router 2, and the WAN port of Router 2 to any port in Router 1.. Then if the specific port is plugged in, I would get...

Sharing two sources of internet with one cable possible?