A Bakfiets type cargo bike with crank drive, with user able to select cadence at which power down occurs. With max power allowed legally.
Disc brakes and perhaps a belt drive, if they can take the additional power from crank drive motor. Rohloff or maybe Alfine 11, I'd like to compare how they feel first.
And/or a Yuba Mundo / Surly Big Dummy similarly equipped drive wise, but with the back end adapted to take 'fatbike' tyres like this;
Black Floyd | Parts | Surly Bikes
So you could have braking to match the weight going downhill with less risk of locking the wheel and skidding. Maybe a dual front disc would be possible.
Disc brakes and perhaps a belt drive, if they can take the additional power from crank drive motor. Rohloff or maybe Alfine 11, I'd like to compare how they feel first.
And/or a Yuba Mundo / Surly Big Dummy similarly equipped drive wise, but with the back end adapted to take 'fatbike' tyres like this;
Black Floyd | Parts | Surly Bikes
So you could have braking to match the weight going downhill with less risk of locking the wheel and skidding. Maybe a dual front disc would be possible.