Ok I'll throw my two leptons in to the ring,
My husband is currently saving to buy a leitra (the velo he was building have to wait untill the temps are higher, 70 ish) the trailer that he bought is from bikes at work, and he was able to use some scrap carbon fiber tubes he had spare to make a mount for a solar pannel. he has thought of mounting a a hub dynamo on the trailer. there would be sufficient space to have a small compact charge controller mounted on the trailer as well as the necessary electronics for the solar panel. I suppose that depending on what a guy/gal would feel comfortable with and what they really need whilst on tour is the deciding factor on weather or not they would be worth it.
Beckieanne