That sounds like a horrid decision. Imagine having to troubleshoot a relative's computer, which isn't working because their internet is down, or is too slow to support streaming Windows like that.
It just sounds like a nightmare all-round, both from a Microsoft Standpoint, since they would have to build all the hardware to support it, people who would have to troubleshoot an issue that might show up on either the local or networked version of Windows, but not both, and from a security standpoint, since it seems like it would make it a lot easier to just hijack the whole computer using that kind of mechanism, with the user being none the wiser, for the most part.