> I am not sure whether non-standard controls would even be allowed, though.
Good point, regulation is a huge issue.
It is my understanding, though, that FAA and EASA are moving away from regulation that is very prescriptive in exactly how to achieve something (which would indeed make it hard to introduce an entirely new control concept) towards regulation that prescribes more what needs to be achieved (controllability, safety, etc.), under the heading of "performance-based certification".
Also, it appears regulators in Germany are somewhat positively disposed towards this, and even considering to establish a new category of aircraft with distinct certification requirements and airmen licensing requirements.
I mean, in fixed wings, you have to demonstrate a certain number of take-offs and landing, which makes perfect sense, but it's not really transferable to this aircraft:
ok, you sit in a Volocopter and then press the switch up with your thumb for take-off for a few seconds, then hold it fully down until touchdown (automatically slowed down when ground proximity is detected), then repeat a few times (up, down), and get your license... :-)