Yeah I think you don't need to do this to an expensive bike. Mechanical disc brakes and just a front shock are probably fine if you want to go 50km/hr. A heavier sturdier frame and burlier tires are ok because it is powered.

I wouldn't recommend converting a road bike as they are more fragile.

I’d love a utility ebike but afaik they just don’t have enough weight and hence - the grip at high speeds to be safe.

I’d guess e-scooter/moped is next best thing tho parking is an issue in some places.

Mechanical grip is entirely a function of tire compounds. In fact, ebikes can have even more tractive grip because you can make them AWD! This makes them much safer in snow and ice compared to other two wheeled vehicles.

They are fine at 45-50 km/hr. That keeps pace with car speed on residential roads fairly well. Any faster and I agree you could look at scooter or moped.