I agree that this design requires a larger number of power transistors. This increases the overall cost. But this replaces a mechanical gear box, plus differential, plus...
And I don't understand why power transistors should be larger than for other designs for similar power motors.
series resistance is the limiting issue with this design.
Things helping this issue:
Larger slow, low RdsON devices can be used (compared to PWM optimized devices)
Things hurting this design:
Way to large a volt second bandwidth across "gears". So components will be large for the worst case.
also current bandwidth is large increasing component size and cost to be able to handle worst case.
Clever and interesting nun the less.