1) Run Android Apps - Yes, this would be the best way forward
2) Run Android as the OS - No, Android is a fragmented mess using three bad OS models stacked on top of each other.
If Android is the main OS it would have no advantages that Windows can bring, like lower power consumption, faster software, stability or security.
Even going back to WM10 - on the 810 SoC - the Lumia 950XL was benchmarking often 2X faster than any similar device running Android. It wasn't the hardware giving it that 2X performance difference.
Android is a problem, even Google knows it is a problem as they are ripping it apart and trying to layer it and strapping everything back together with duct tape. (Go read any of the work on P and beyond. Windows is already tight and without these issues.) As an OS Engineer/Educator Android looks like a junk drawer with various pieces duct taped together to be more organized. The current work Google is doing now is adding in a couple of plastic trays, that have broken slats and adds more duct tape.
The idea that an aged and horrible OS like Android is used by so many people today is an embarrassment for the entire technology industry. We should ALL be ashamed we let this happen, and we should have forced Google to stop the crap as Android was first shipped. We forgave Google because Android was new and Google didn't understand OS technologies. Then it was too late, and they are giving the world the finger as they continue to produce crap.
Stability - This is a bigger problem than people realize. How many times do you have to reboot for Bluetooth or XYZ App to start working properly? Or WiFi or pick any of 100 reasons why Android devices are restarted on average 1-2 times per day. (In contrast WP8 and WM10 devices are/were restarted once a month on average.)
The stability issues with Android also create a series of dependability and reliability issues. Notifications not firing, Alarms not firing, communication tools not firing.
The Android stability issue isn't just 'crashes' it is HOW ANDROID'S PROCESS works, as it will close Apps and supporting tasks that cannot be restarted properly. It will even close Active processes like VOIP software while it is in a call if a background process or new process needs more RAM. There are times users don't even realize that Android itself screwed them by closing their App for a stupid reason.
Performance - This includes battery and App performance. In addition to the 950XL example - Android still doesn't do Big Little core management well, still doesn't throttle background tasks properly, still doesn't handle thermal threading, still doesn't use the GPU and GPGPU operations more, still can't seamless or agnostically thread to various cores/processors on the device. - All of these things are now inherent to Windows.
Subsystems - Windows can already run Linux in a subsystem, as this is how NT was designed and how OS/2 1.x and POSIX originally ran on NT. WM10 was supposed to have Astoria - which was Native Android Apps running on WM10 - but with the benefits of WM10 and NT.
Microsoft can still technically do this EASILY... The problem/trick is Google - they changed their terms and started moving their services from OSS and a license that allows that to pick and choose who can use it - Google is playing dirty, and this is another reason Android needs to be broken or taken away from Google... Even with Windows being Closed Source - Microsoft has never used it or leveraged it like Google does with their parts of Android now. (Yes I say this with full knowledge of the Monopoly ruling - as Google is beyond the tiny things Microsoft was accused of doing. Go ask Samsung, or HTC - they will tell people this, as Google has leveraged their control of Android against them, and Samsung was a key to Android's popularity.
Surface Phone/Tablet (Whatever it is called) needs to be Windows to be fast, stable, secure and ironically open. It also needs an Android Subsystem at least to start out, with a better migration set of developer tools than what Microsoft has now, as in fully automated to get developers ok with their App running on Windows in the Android Subsystem and give them a One Click way forward to make it native to Windows.
This thread and idea it should run 'Android' as the main OS is one of the most ignorant things I have read in a while, and I hope Microsoft isn't this stupid.