I also like the idea of one battery to charge instead of multiple batteries to charge. Though by the time I decide to get a new bike, I might not have that choice if I want the latest and greatest of that time. So I won't bemoan it that much and just get what's available then. Whether it's 1, 2, 3 or 50 batteries!
Two batteries and there is twice the chance that I'll ride with one of them not able to do what ever it's supposed to to.
Or am I understanding you to say,
PeteHski , that SRAM can work all the components from one battery when one of the batteries is dead? I didn't think they were connected.