Microsoft has all the expertise in partnering with vendors and getting them to ship their operating systems, they have a rough idea about how to run an app store and they have access to developer. A de-Google, privacy focused Microsoft Android, with a Microsoft store, the ability to run native Android apps and perhaps .Net application, pushed by Microsoft sales and vendor channel seems pretty interesting to me.
But Microsoft doesn't care about neither privacy, nor mobile and practically no phone manufacturers really care to ship anything but Android at this point.