1WD hybrid no harm to driving both sides, the pedals already do that.
The only challenge there I see is that pedals are generally kinda lower power so you can get away with a sprung chain tensioner. you can't pull the wheel back to get tension equally on 2 chains the way you tension the drive side, unless you're real lucky on length. Anyway you'd need a strong enough chain tensioner on the pedal side.
I think the weirdest part is where to fit the electric motor. Maybe on a rack would work, but the chain length'd change significantly as the shocks compress so maybe it's not such a good option. But in the stepthru cradle or something your chain line's gonna be a challenge too