And my brothers bike bites my posteriour again.
He uses a not so cheap Merida (he didn't pay for it), with a Sram Eagle 1x12 . But after using a 500W Bafang BBS02b for a while , he asked me to install a Bafang 1000W BBSHD.
After a few 100km, the back wheel started desintegrating. The cassette was eating gears and getting wonkier by the week. And not long after that, he was having spokes ( light laced wheel with 24 spokes) popping like popcorn. So, he's not willing (not unable, he's not that stupid) to learn to do anything mechanical himself (the antithesis of the Atomic Zombies), and not willing to spend a load of cash, it was up to me to find a budget and maintenance friendly solution.
My answer. You going all out, with the Bafang doing its level best in torque, the only drivetrain, realy cheap, reliable and maintenance friendly, is a single speed.
But alas, he wants gears, the more the better.
So, I ended up installing a Nexus 8 with a 36 spoke double wall rim.
Today , that poor hub will have the first taste of abuse...