The Verge reports that Microsoft is considering taking a page from Google and giving away Windows Phone and Windows RT for free to device makers in the hope of grabbing more market share. Microsoft would see revenue through other avenues, like ads and services like Skype, SkyDrive and Bing.
That model has certainly worked in the past for Microsoft. That's how it made Internet Explorer ubiquitous (and destroyed Netscape in the process), and Google has used that model to obtain an 81% market share, according to IDC.
On the flip side, there is also a ton of mediocrity on the Android side. There are a whole lot of Android tablets and phones not worth the plastic and cardboard box they come in.
Would it work? I'm not so sure. You want the top-tier Android phone makers, which translates to Samsung and the rest. Do you think Microsoft would not have struck a deal with Samsung if it would have gotten more WP phones out there? LG was a WP licensee and gave up because it saw no market. That was a while ago and the market is shifting, slowly, to Microsoft's favor.
What I would do, were I running the WP group, is conduct certified ports of WP8.1 to the 5-10 most popular Android phone models on the market, then make them downloadable installations, so anyone can download it and load it on their Android phone, thus erasing the OS install. There's no risk of loss, since most phones have a factory reset that reloads the OS and people can go back to Android if they want.
This would let Microsoft bypass the recalcitrant OEMs and let users hack and experiment. Because of the closed nature of the OS, people wouldn't be able to download and tweak it for older phones like they can with the open source Android, but it's worth a shot.
So if users of the Samsung Galaxy S3 and S4, LG G2 and HTC One could download a big file with installer and all they need to do is connect to the PC for about 20 minutes and wait, that would get Windows Phone in a lot more hands fast, and it would get the attention of the OEMs, which Microsoft seems to have lost.
IDC has defined the relationship between Microsoft and Nokia as mutually dependent; Nokia has no other OS, although rumors of an Android phone abound, and Microsoft has no other OEMs. Microsoft needs more OEMs and the best way to get their attention would be a large number of users replacing Android with Windows Phone.