When a pebble hits underneath my skateboard the reason the skateboard stops and I continue is because ME moving was why the skateboard was moving. In the case of a powered wheel I'll hit the pebble and keep going and keep going, sense the wheel itself is still turning.

I repeat, the wheel is turning, not being turned by inertia and friction.

As for the breaking, I can train myself to lean back when I hit the break, and lean forward when I hit the accelerator. It's not that hard.

PS: I would hope to Jebus that someone would be wearing a helmet and other protective gear with this.