Apk extension files for self service

I am working on an Android digital library application and would like to provide collections of selected resources in different languages ​​- one collection in each language - ideally like apk extension files. I understand that I can have a maximum of two APK extension files using the Google Play Store.

This is a two-part question:

• Is there a way to host the .bb files on my server?
• If so, is there a way to select a specific .obb file to use? (In the user interface, apps offer the user a choice of languages ​​to get sample content.)