This is less efficient than putting all the batteries and other gear on the frame, right? Spinning all that mass around will take energy. I don't see an advantage unless you expect to swap wheels out often.
The Smart Wheel actually consists of two halves one of which is fixed (it doesn't turn). The battery is therefore stationary and doesn't require any kinetic energy to be spinned around the axis.
But from a business perspective, people who care about their bikes enough to spend big coin often care about the way they look. And attaching a battery w/ leads to an electric wheel is a major buzz kill imho.
