Having used ModernMix and Start8, I am convinced that they would only be doing a service for a large number of their users if they fully restore the Start Menu, and allow windowed-mode Modern UI apps running on the desktop. Stardock got it completely right with this mix. They have purportedly worked with them in the past, and I do not see why they would not or could not do it again to bring these features back into Windows. Once you are 1) not on touch screen and 2) have the start menu, the next logical conclusion is that you realize you can run the Modern UI apps on the desktop and they behave virtually exactly the same, with no loss in performance. Once this is realized, the whole idea of the Start Screen comes into question as to what the point really is.
Now you would have the option to run either way. Personally, I have to say that having the Start Menu and the features of ModernMix to run Modern UI programs on the desktop in windowed mode is the ultimate solution for me, and I would even consider using such a platform with a touch screen-enabled device. I do not see any reason to limit consumer choices in this area.
I suppose returning the button itself would be kind of pointless as the full menu is needed at the very least for many users. I identify this issue with people who continued to need to use classic shell when Windows XP came out just to get around (they found the interface untidy and difficult to manage). I believe it is more-so evident in this case and they really should just come about face, look at what Stardock has done, and license it into Windows. They have done it with defrag and a bunch of other features so I don't see why they wouldn't do it here. Start8, alone, is listed as the #1 desktop customization program on CNET. This should say a lot as to what people are upset about with Windows 8. Outside of this issue, the operating system works and functions great and is far more stable and reliable than even Windows 7.