In my mind there's a "standardized", probably cargo, e-bike that has not yet been invented. A e-bike (or scooter) that is mass-produced and inexpensive like the Volkswagen Bug and popular enough to breed an ecosystem of aftermarket parts, mods, etc.
Let the clones follow using the same parts, connectors and you could have a world-wide phenomena.
I bought a sit-on electric Chinese cargo scooter from an importer in Bulgaria because I liked how it looked, and it's handy for going around town. They are everywhere in China. They are assembled by hundreds (probably thousands) of small factories. A big center is Wuxi. I visited a few factories there last year. The scooters cost about $350 USD in China.
There seems to be a sort of loose standardization around components, that are also churned out by countless factories. Wheels/motors are generally 10" or 12" size. Brake disks have either a certain 3 or 4 bolt pattern. I'm sure the electrics likewise follow some patterns.
I had the thought that it would be fun to 3d scan parts, measure and document some of these scooters, and make a database of suppliers. Then, who knows, start to make the frames and assemble in Bulgaria.
But you really need to be spending time in China to do that, and it wasn't really the right time for me then.
Another thing to note: branded scooters (niu etc.) are becoming more popular, better quality, extensive plastics, and you can probably order parts from the manufacturer.
Let the clones follow using the same parts, connectors and you could have a world-wide phenomena.