It is difficult to see how a registration scheme will ever work. These big toy UAS are bought by MTV watchers who take breaks to play call-of-duty and grand-theft-auto. They will not be aware or care about an FAA regulation nor will they hear about large fines imposed as MTV won't carry that and if they did call-of-duty would be played in preference to watching a talking head.
The toothpaste is out of the tube and the ANSPs have been far too slow to act. It was apparent 10 years ago that this could become a problem just with normal full size commercial UAS and model aircraft with payloads. But the bureaucracies preferred to just not take notice and wait out the commercial pressure that would 'go away'. Except it didn't and several enablers became available concurrently, small GPS, powerful small electric engines, and, control electronics for stability of multiple rotor UAS. Suddenly as the draft regulations for sub-55# UAS were being published the world wass flooded with grown up toy UAS being sold everywhere from traditional model aircraft shops to literally anywhere - I saw some in Bed Bath and Beyond.
Even if there was a bad crash due to a UAS/airliner collision, the use of UAS would not be affected there are just too many of them. Standards, regulations and laws could have been in place years ago, but it was easier to just say no. The toy UAS was not considered as ANSPs thought all UAS would be Predator like and need a large commercial organization. Not something that can be bought anywhere and flown by an unsupervised teenager.
The ball was dropped 10 years ago.