Currently mentoring a startup in this space (not in the UK). For us it's because of mandatory insurance for 3rd party liability, and as a non-drone owner who's seen plenty of idiots wielding them, I'm all for it.

I prefer the light touch (ala Mopeds/Scooters) where it's simple and easy, insurance at a flat rate, easy to transfer ownership. Something akin to cars with a v5 document, etc would be overkill.

I don't really have an opinion on the weight limits, how much does something have to weigh to take out an eye, or cause a motor vehicle to crash?