Yes, and I think your theory is both admirable and completely sound as a starting premise. I'd love to see thousands of these replace thousands of cars, in theory. I'm just not sure (looking at the evidence in Paris) you can then trust legislators and authorities to set the right rules and environment, even less enforce it.But replacing one-person transport with a 5kg payload over one-person transport with a tonne & a half payload has to be a no-brainer doesn't it? We can fine-tune the rules and regs as we go along. And realistically it'll only ever be a marginal help (most people will still prefer their cars). But every little helps, no?
Look at policing and enforcement in the UK: We've become so car centric that the police are now largely car centric too. They mostly set out on their shifts in their cars, and they react to incidents in their cars, and on the rare occasions they're not doing that, they might look for car related offences, albeit only sexy ones. They're not really effectively addressing things like phone / internet use at the wheel. They're not out walking or riding the street, policing poor scooter or cycle use and offences, they're not even being proactive on burglaries. If it's not something sexy happening in a car at high speed, they're pretty blind to it.
Give people a chance to be low-level lawless with no chance of penalty and many of them they will be. Unfortunately I think in modern society it's not as simple as changing / tweaking the laws, you have to be able to enforce them.