I haven't added any fault tolerance. Should be fairly easy to detect if a route is unavailable and re-write the routing table. And yes, I expect the Pi is still a bottleneck.
Is there any embedded hardware that can handle 140Mbps line speed without being maxed out?
Something like the Cubox-i/Hummingboard should do the trick. It has a beefier CPU and a gigabit ethernet interface that isn't attached via USB like the one on the Pi/Pi2.