You're thinking on the right questions..

It took years, but finally I realized the appropriate threshold is simply to have people go on an exercize-bike/meter, for a 90-minute-session, & have them sustain what they can, for that duration, then multiply their RMS-output ( root-mean-square rounds-down ) by 3x, & make that THEIR motor-limit:

This means that you don't get flimsy 50-lbs children with 750-w of bike-motor, & you also don't hobble linebackers ( I think that's what they're called: NFL tackles? ) with the same limit you're putting on small/flimsy ones.

Proportionate to the strength you wield when managing your own body, see?

So, for many reasonably-strong riders, it'd be .. around 300-w, tbh..

Alot of people would hate me for making the limit sooo close to their own physical-strength, but .. live longer.

& simply make another limit, higher, & require license-plate for that category.

I'd make it so that within the 25-kph & 3x-sustained-90-minutes-wattage, no license-plate is required: you get a photo-ID card which says you don't need a plate.

More power, more speed? then you need a plate.

Some cities need 40-kph to do the parkways, & that'd have to be one of the limits.

60-kph would be needed for other parkways, but that'd be absolute-limit, & some body-armor would be reasonable at that speed ( since crash-energy goes up with the square of the speed ).

Having been a courier, I'd put an either-speed-XOR-weight limit on them, so the fast-light people can get that, but the heavy-cargo couriers get a slower-speed, .. I"m not the only courier who discovered that it's .. an experience that many couriers have had .. to discover that one has been biking, in traffic, while unconscious. Sleep-biking. And I want that NOT happening at high-speed.

So, this is all like graduated-licensing, but done vertically, instead of temporally.

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