MDM supports adding enterprise apps as Private Play Store apps directly from the MDM server via Managed Google Play. This method does not require you to pay any fee to register with Google as a developer. When you publish a private app for the first time, Managed Google Play automatically creates a Play Developer account on behalf of your organization. Refer to this, to know more about publishing private apps in Google Play Store.
Google has introduced App Track Management to manage multiple versions of apps through Android for Work. App developers can add new versions of an app as tracks and make them available to your organization. MDM provides you with the ability to test and deploy any number of custom releases before releasing the production version. You can publish apps to custom testing tracks on the Google Play console, and then distribute these apps to devices.
Multiple versions of google hosted private apps can be added to the App repository, by following the steps mentioned below:
The pre-released app versions will be added to the App Repository and can be distributed to the managed devices as explained here.