Solving the safety problem by making it loud does not seem like a great solution.
Fast forward and everyone is driving nearly silent electric vehicles. I wouldn’t want loud Vespas then. Cutting city noise pollution is one of the benefits of electric vehicles.
It's not a great solution but it's the best one I've got, and it's still more ecological than driving the (electric) car for the same one-person trip. And audible != loud.
Anyway, don't most places legally require nearly silent electric vehicles to emit some kind of artificial noise?
Should license movement noises from Hanna-Barbera. Jetsons or Flintstones are good, but there's probably other options.