The crank will have a standard 130mm BCD bolt patern. So, the smallest chainring would be 39 tooth. I could add holes for 110mm BCD as well if I get requests for that. 3 chainrings can fit (remember, one chainring is for the electric drive). With freewheeling cranks, most people use one chainring for the rear drive and one for the motor. So, a dual drive hub system is best for more than 9 speeds. But, again, 3 chainrings is possible. As for Schlumpf drive, no, that uses its own crank. My system requires a freewheeling crank. Of course, you could choose not to use a freewheeling crank. But, then the cranks will be driven when the motor is running.
1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?