It might work without a throttle, but some controllers had a fail-safe mode where the cruise button could be pressed to provide half throttle if the throttle failed.
If you unplug your throttle and the pedelec still works, you won't have to worry about the throttle fail-safe mode.
A 10kOhm potentiometer could be used as a throttle, but as there is no return spring to close the throttle, you would need to wire the throttle signal through a momentary push switch to ensure the throttle can't stay on unintentionally, and also to prevent the motor cut-out safety feature from activating when the power is turned on when the throttle is not closed.
If your controller has the throttle fail-safe function, you will need a 12kOhm resistor between the +5v and the signal side of the switch to prevent the throttle fail-safe mode from being activated.
Alan
