Stardock only scratches the surface of the Windows Operating system. To go from 'flavoring' windows to a full blow operating system is like saying you built a model plane, now you can manufacture aircraft.
There is SO much that would be nearly impossible to do without MS suing you, or getting public acceptance in the mass market/ compatibility it would not be a job anyone would attempt. Not in the market as it is today. Nice to think about though.
I would like to see the Android OS compete, but I do not believe it will ever happen. They will be stuck with cell phone and mobile devices.