That's a great idea. How about some induction charging on the bands? Watch ran out of battery? No problem, change out for another band. They would have a induction charging plate for you to just lay your watch or bands on. 😀
Want to wear your watch while you sleep? No problem. If you wake up with low battery, change bands.
It's like having a camera. Just swap out batteries if you need. If only Apple thought of that for the iPhone.