Not saying it's not the right choice, just saying maybe you want to look again... I was leaning strongly to a mid-drive until I started thinking about all the power going through the rear cassette. Was not really meant for that and may break eventually (mid ride) ...
So I'm now leaning toward a rear drive geared hub motor (Bafang). Same motor and internal gears as used in the BBS series, but driving the wheel directly. It'll freewheel coasting or just pedaling, so if the electrics go out, just ride home.
I'm looking at advanced pedal assist (PAS) kits from Grin Technologies based on a G3xx series. This way the pedal input adds the motor and the cassette still only sees your leg power. The wheel sees it all, just not the cassette.
I want a crank torque sensor in the BB so that as I pedal more firmly, the motor adds more proportionally. It's stated to feel more natural and makes sense to me.
Maybe look a little further ...
This way you have no over-torque into the cassette, but all the gear reduction advantages of the BBS series. Shifting will be more natural as you are still doing it just as you would with a pedal only bike
