For me Apple choice for ARM/OSX is
they see the CPU and GPU only as a part of there system-on-a-chip (SoC).
If you look at the evolution of A-series there is more and more integrating specific hardware for a specific task .. like the camera, security, specific software acceleration and so (maybe in next 2 generation the complete integration in there SOC of the in-house (ex intel) G5 and network module )...
which they tiedly integrated with there operating system.
There is also a economic part to reuse some mobile in-house developed hardware modules in the mac computers or soc.
I'm sure Intel will have a better core and maybe in the near future a better power package and/or lithography than TSMC.
But Intel will not let Apple integrate there additional hardware modules in there soc.
How to VM these specific future hardware of Apple on a general use Intel based computer without damaging the user experience of OSX i don't know and maybe does not make sense.
Even if I share the authors dream to have OSX working nicely on any VM or x86 hardware.