why not (mostly) a mesh network made up of the individual cars themselves, with a few connecting to the actual internet and acting in a sense like mobile cell towers? the cars would probably vote on which one in a vicinity was going to be come the next "hub" based on some algorithm accounting for location of surrounding cards, location of its own access point, as well as info about its likely route & destination.

Why not let the cars can talk to eachother, and through eachother to the outside world?