> "E-bike" is pedal assist only/mostly with max speed of 30kph/20mph (only while pedalling) and throttle cuts out at low speeds (7kph: basically just there to get some inertial); treated as just another bicycle (perhaps limit age to ≥14 yo). Everything else is an "e-moto" with the same rules as mopeds and motorcycles.
I'm going to respond to this pragmatically.
Realistically, the current Class 1/2/3 system more or less works.
Class 1 is pedal only, max 20MPH (but lots of bikes are sold as class 1 with lower limits, I think the one I got for my chosen sister is 10, maybe 15 tops.).
Class 2 is Pedal+Throttle, max 20MPH. Again, sometimes the manufacturers will have a lower cap (Wife's e-bike has a throttle cap between 12-15.)
But 7KPH is too little, at least for the US if you want to get more than low rate adoption of E-bikes as a mode of transportation [0]. At bare minimum you need something where the person can maintain balance and it's faster than a brisk walk.
Class 3 is, well I thought it was Pedal-only 28MPH but I think there's some conflicting data and hand-waving. i.e. some claim that Class 3 is 'throttle up to 20MPH, pedal assist up to 28MPH' but last I was aware a Class 3 shouldn't have a throttle.
But again, the confounding factor [0] means that some compromises may have to be made.
The worst part about all of this, is everything was more or less OK, until these e-motos and overpowered e-bikes went on the market, and parents bought them for kids without any thought of risk/etc or even paying attention to the 'offroad use only' disclaimers. I also put it that way because (sadly) if it was just adults getting splattered it would probably just get treated like any other motorcycle/cycling accident as far as actual action.
[0] - As a confounding factor, I'll give the example that in my state, an electric scooter qualifies as an 'electric skateboard' and thus so long as it has a throttle cap of under 25MPH, sure, go nuts unless there's a restriction via muni (e.x. some munis may ban use on roads with a speed limit over X mph) or DOT (e.x. public highway restrictions.)