If these devices are flown by a pilot of some flavour then I can't see a problem. The pilot should have been taught air law, should know what is right or wrong?
It's the unmanned variety bought by Joe Numpty flown with no knowledge of the existence of air law, rules, flight safety, or whatever that are the problem.
People have killed themselves for decades experimenting with new ideas, end result, we survivors end up with 747s to take us anywhere and safe little aircraft to play with. Development is unfortunately sometimes expensive. But how else is progress made.
As new things are invented some regulatory outfit seem to insist on it having a designated category that "fits in".
If I were to invent an anti gravity, electromagnetic system that could take off from my backyard in silence, fly to orbit at Mach 3 circle the international space station and return without using any fuel, what would the "class" be?