Your first three paragraphs are sound.

But surely the problem with the final paragraph is the transition? Assuming the old style of vehicle remains on the road, then my lightweight one is at risk of being crushed. Only a niche minority would choose that (as a cargo bike owner, I'm also one, but I recognise most are not, with good reason.)

Unless we built a whole separate infrastructure.... We already see a lot of electric scooters using cycle lanes.