Jim, you keep going back to your same idea -- which 2 pages of responses have told you that it's unrealistic for several reasons (which I'll summarize):
1. RV lights run off the 12VDC side of the house, but aren't usually stable enough to be reduced down to 5VDC to meet USB specs.
2. Most lights are mounted overhead, which isn't a safe place to have charging cords hanging from (snagging while sleeping, accidental choking, etc.).
Go with Dutch's or Roy's suggestions; they're workable without the safety hazards. But, don't hold your breath for the lights! Wanting won't make it so.
