> In that case other companies, say, Micrsoft could then start to offer a $100 Android version containing Edge, Bing Maps, Hotmail as services.
Just like Microsoft offers a $100 iOS the same way, right? All you're asking for is for Google to stop developing Android for free. Then Google's version becomes macOS to the legacy Android's FreeBSD, or WINE trying to keep up with every change to Windows.
It would make it harder to develop an alternative to Google Play than it currently is because then you would also have to produce an alternative to Android.
And it does nothing to solve the actual problem, which is that app stores have network effects, so users won't use one with no apps and developers won't use one with no users. Even ignoring Android, suppose the value of Google Play to the OEM is $50 and the value of being default to the highest bidder (e.g. Microsoft) is $20. Then the OEMs have been getting a discount of $30 to get both for net of zero.
Now suppose you price them separately and Google offers Google Play for $35 and pays $35 to be the default. The result is exactly the same. Google Play is worth $50 to the OEM over alternatives, costs $35, so they net $15 by choosing it. Google Apps pay $35 when the alternative pays $20, so they net $15 by choosing it. No change in behavior at all.
If you want to actually fix it you need to break the network effect, e.g. separate the Google Play service from the Google Play app, so that anyone can build a store app that can install apps from multiple stores (even if OEMs still have to pay for access to Google Play). Then explicitly allow app developers to pass the store fee onto customers using that store through differential pricing between stores, so that the same apps from stores with lower fees actually have lower prices. That's how you get more stores, which is how you break Google's leverage with the Play Store.