That's why you use mesh networking. Everybody participates in the mesh and provides a path to other nodes. I used an OLSR network to allow the locomotive on a long train to pass messages both ways down a long train...even if it was wrapped around a mountain. A line of sight 802.11b can pull off a 1 mile link with off the shelf hardware. I've used custom hardware with bigger power amps on a large airplane to achieve links over 50 miles.
Wow that is impressive! Would an amp that big (airplane) interfer with normal household electronics?
If not your mesh concept has serious legs.
It still would be difficult to implement though. You would need static routes defined to route traffic to the mesh network, assign IPs, etc. Most people would have no idea how to integrate into their existing network even if they wanted to.