How good are you at hacking? It's possible to reprogram the walk assist speed so that the walk assist button works like a full-speed push-button throttle. Without hacking, you need the Bosch software, cable and password to do it.
I think you need to look for something other than a crank drive
Non of them are designed to work as throttle units
If I was you I would look into hubs instead as it defeats the object of the crank drive to have a throttle
You should get instant power just by pressing the pedals; one advantage of torque sensing. Maybe not as much as you want though? Or at least, instant torque.