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Having the motor casing drive the edge of the wheel is clever since it provides the necessary mechanical advantage without gearing.

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“While it would have been nice to engineer some sort of spring-driven mechanism to control how forcefully the motor pushes against the tire, I kept things simple: I just deflated the tire somewhat, bolted the motor solidly in place, and reinflated the tire.”

I think Solex (https://en.wikipedia.org/wiki/VéloSoleX) did that better.

It uses the weight of the engine to press the powered wheel to the bicycle wheel, accounting for variation in wheel diameter due to tire pressure or tire wear. This could use the weight of the battery pack

Assuming his motor is mounted tight enough so that the tire loses traction before his friction drive does, he's likely halving his tire life.

That's fine for a project, but hub motors and mid drive motors are widely available now.

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