I always though the simplicity of bothies were key to their charm!
It's quite nice to get away from tech and electronics but still have somewhere sturdy and dry to sleep. I kind of feel if you're looking to stay somewhere with more electricity than one can carry in a power bank for phones and headtorches you might as well stay in a proper hut!
Adding solar cells (or even wind power) to a bothy would be very doable, but I'm not sure its what everyone would want. In terms of keeping solar cells snow free the best system I've come across it just someone with a broom!