You know... I'm just thinking loudly here.....
How hard would it be for Amiga to license a "prt" of OS4.x for the Wintel market?
If needed... mayhaps an Intel-compiled ROM on a PCI addoncard, which would be required to run the OS on you bog standard IBM-PC? (I have no doubt some person would hack and slash and make the addoncard "emulated" on a file on the HD at some point, but still
) For the initial graphics... heck, both X and Windows are nowadays capable of showing 1600*1200*32bit, completely unaccelerated. Then you could mayhaps get AmigaOS4 drivers for .... say... ATI Radeon series? (Seeing as ATI is supposed to be easier to obtain required data from to make drivers than nVidia)
Then... on the addon card... some kind of sound emulation system, nothing fancy... Soundblaster 128 would be sufficient for "starting the OS with sound" then I believe Aminet's "Hard/Drivers" drawer would be crammed with homemade drivers for other cards after a short while. Then with these new (AHI compliant?) sound drivers and card, you could disable the addoncards' builtin one.
And of course... don't forget, WinUAE comes around with AmigaOS4UAE and integrates almost seemlessly :P
I really don't see the big problem, other than to get the neccessary license and someone to do the dirty work of the porting.