The best option may be a BBS01B crank drive if the bottom bracket housing is a standard 34mm dia.
You would loose the 3 x front rings but will have full throttle you can use, though controllers can be a bit flaky whether they are reprogrammed or not.
Another option is a GSM mid drive without integrated controller and use a separate KT controller and LCD3 with full throttle enablement or set it legal for throttle once pedals have turned (1/8 - 1/4 turn is all that is needed).