Well VA (which you mentioned) *only* runs on Windows. To use VA effectively you need windows. It isn't a simple matter of "freeing the OS from its ARM roots" as the roots go rather deep (much of the OS is written in ARM code and you can't easily transfer ARM to x86 as the code is different the number of types of registers differ and so on). The OS is has an intimacy with the underlying hardware (which differs somewhat from that on the PC) unless you opt to port RO5 and that (even with the HAL) would be a bit of a steep climb.
ARM is gradually improving its performance and even countenancing larger caches and changes in architecture to improve performance. So perhaps we should be too *quick* to ditch ARM just at the moment - any switch would involve considerably more pain and probably not a lot of gain to boot.