Something to consider is maybe that 500w mid drive is not the right answer... but for a different reason than power output. I'm not speaking of a manufactured ebike here, where I assume they've thought this through and dealt with the issue. But if you have a choice of installing, lets say, a BBSHD, or a BBS02 (or a Tongsheng TSDZ2 for that matter) then there the construction of the motor itself when subjected to heavy load should be considered.
You can kill a BBS02 if you work it hard enough. The controller can fry, most typically. This is not as much of a problem as it once was, but its still something to keep in mind. I've also heard of some Tongsheng users having trouble with a little blue gear inside that can die an early death if the motor is worked too hard. On the other hand, a BBSHD was built as the heavy-duty successor to the BBS02 and its bits are more robust to the point that you can't break it unless you hotrod the thing with something like a 50a aftermarket controller and say a 72v battery. So for normal folks using it within factory limits... its essentially indestructible.
I tone down my BBSHDs' output on pedal assist as I don't need that much power, either. But I am very happy to have motors that are overbuilt that I can rely on.
