Having to hold licences which are themselves illegal on the aircraft in question?
Those licences have about as much relevance as holding a train drivers licence alongside your flying licences and then having an insurance company refusing to pay out on the fact that you dont hold train drivers licences.
Yes; it is mad.
But it is objectively no less mad than requiring the
carriage (the regs don't specify the
use of) an ADF for IFR enroute. Or requiring the wearing of brown underpants; in fact those might be more applicable to some types of flying than an ADF.
IF, when all this comes to pass, I can get my insurer to confirm I am insured on my FAA papers alone, I will be happy to fly with that. But, I have found, insurers refuse to spend money on their own lawyers, and they even refuse to spend their own time to think about something you ask them. They just say you have to be "legal", which leaves them with all the options, which is exactly how they want it.