Problem Definition: We have a fairly large app which has multiple use cases such that they are all independent of each other. For example lets say we have a1, a2, a3 & a4 modules that are independent apps or use cases for our main app 'A'. The independent a1, a2, a3, a4 are all purchasable apps such that the user goes to our website instead of play store and activate either a1 or a2 by paying some fees on our website.

So basically App 'A' is a free app in play-store and is sort of Dashboard with buttons to launch a1, a2, a3, a4. When the user click on lets say a1 button then we will check if a1 is already installed and launch it but if it is not present then give the user a link to download it.

Option 1: Have a main app 'A' and a1, a2, a3, a4 as library project. But with this approach the main app A is too big in size.

Option 2: Have a1, a2, a3, a4 build as separate .apk and then put in the assets folder of main app 'A' and then install them as needed. Again size of main app A is bigger.

Option 3: Upload a1, a2, a3, a4 to a third party website or play store and download from it as needed. This way the main app remains lighter.

Observation: In all these approaches there will be an independent app installed with its own icon on users phone. So basically user can launch from either the Dashboard (which will eventually launch an intent from Activity in a1 app) or user can directly launch app a1.

Follow-up Question: Is there any other solution that anyone can suggest to tackle this kind of problem? Another things is by going this approach app a1, a2, a3, a4 can be developed & tested independently of each other.