I would recommend you fit my mid motor 48V BBS01ET and modify the rear cassette to keep the front to rear ratio low and torque high. You have maximum 100NM at the 44T chainring, so if you fit 22T, 24T, 26T, 28T, 30T,34T, 36T, 38T, you'll get 50NM, 54NM, 59NM, 63NM, 81NM etc