I have an application where it is three layer

1st layer- A legacy core routines
2nd layer- built on top of the Core routine using Dotnot framework.
3rd layer- built on top of .Net framework used for front-end using Android framework.

So, now we have customers using the android applications with different versions. some of them are in older versions and some of them are in latest.
Most of the customers are pushing to use MDM- tools for there usage and they want to deploy the APK through MDM from there private play store. right now we are providing APK customized and built for each customer.

But this have become messy job. we can’t keep doing this.

I require suggestion or solution we could use to deploy multiple version APKs with same package name so that customers can download the specific versions of their choice. and keep it in their private playstore.
Note: Google playstore doesn’t allow to have different versions with same package name.