The thing is... they've tried a lot of this. They've paid developers to port to Windows Phone before. It wasn't enough. They'll practically give you free hardware if you tell them you're developing an app. Realize that Google and Apple do not give a crud about you if you develop an app for their platform. Microsoft will fall over itself trying to help you if you develop for their platform, even if you are a little guy making a little app.
Microsoft already HAS developed the ability for Windows Phones to run Android apps. (They actually sent me a free phone just to test the feature!) Sadly, they decided not to release it, and we don't really know why. It could have been that they were worried about developers settling for Android apps instead of making UWP apps. Or Google could've threatened them, which seems plausible too. (Android is kinda "open" source, where yes, it's open source, but Google will do underhanded things if you dare to use it in any way they consider a risk to their dominance.) I can tell you the Android Bridge for Windows Phone worked amazingly, and my demo unit phone still has that version of Windows on it.
The other name it went by is Project Astoria, you can find a lot of the Internet about it. There's pretty much no chance of it being released at this point, unfortunately.
Microsoft and Google each have subtle and not-subtle ways of attacking each other. Google doesn't really feel threatened by Bing, everyone thinks Bing is a joke (even if it is pretty decent), plus Google steals all their best ideas from Bing. But things like the popups Google has on their sites to tell Edge users Chrome is better, Microsoft's retaliatory popups in Windows that tell Chrome users to try Edge, etc. Google has aggressively broken compatibility of their various services with Windows Mobile devices before. They definitely have options if they want to harass the others' customers.
Microsoft already HAS developed the ability for Windows Phones to run Android apps. (They actually sent me a free phone just to test the feature!) Sadly, they decided not to release it, and we don't really know why. It could have been that they were worried about developers settling for Android apps instead of making UWP apps. Or Google could've threatened them, which seems plausible too. (Android is kinda "open" source, where yes, it's open source, but Google will do underhanded things if you dare to use it in any way they consider a risk to their dominance.) I can tell you the Android Bridge for Windows Phone worked amazingly, and my demo unit phone still has that version of Windows on it.