In the States we have used 802.11 to send damage assessment video from mobile units to incident command post and also to send TCP/IP data from mobile data terminals in our public safety vehicles to the ICP, and to connect via the P25 radio system into WebEOC, which is the incident management software used by most state, local and the federal govt post 9/11, for regional and operational area coordination.
Wifi is designed to be local and you won't get around that. However all protocols are designed to be layered and the phone system, with its longer range is still just another protocol with a node that can be connected to your TCP/IP network. TCP/IP will also run over radio so you can connect some distance. Thus you can have spots, phone areas like we do now, connected together by Ethernet and Radio. The phones won't handover as they move areas but you should get a reasonable range and be able to connect to anyone that is on that network and it could be as wide a network as you can make it with each area/user having a node. Plus with WiFi piggybacking you can extend the spot size in the directions you want to meet outlying homes.
It's all about the base unit connectivity unless you are an electronics expert and can modify it. This sounds like a project for one of these volunteer organisations.