Adventure Cycling seems pretty hep on e-bike touring, but so far they have only travelogged e-bike day rides or inn-to-inn tours (NTTAWWT) and haven't revealed any secrets on e-bike camp-tours.
Just for fun, I mapped out a near-month-long tour here in Parts Unknown, riding from State Park to State Park and camping in sites that have an electric outlet (those costs a bit more than sites without electricity).
The biggest issue is charging the batteries, like you say. I think someone's going to come up with a way to charge them while riding, kind of like what they do with car batteries, only improved.
Charging while riding. How exactly would that work?
Fun fact: the US Patent Office will not accept applications for perpetual motion machines.
