Currently, the throttle overrides the pedelec sensor, so your wishes are fulfilled
Unfortunately, this is not according to the EPAC standard so the current BAC-28X controllers are not fully compliant to EU rules (pedals must be turning in forward direction to let the motor run).
I believe the best would be to have a switch that could be used to override the pedelec sensor. That is actually allowed, but only up to 6 km/h. If this maximum speed was software settable (in flash) it could be as simple as pressing and holding this button to activate motor without pedaling.
Per