Say, you have an iOS app which is fully functional. Then you need to add a feature but it will make the app way too large. So you decide to design the feature to be as a second app which the user can download and install separately but this second app has no stand alone functionality. I mean it is useless without the main app. The main app will start the second app by throwing a URL scheme with some custom parameters. Then the second app starts as the user wants.
Question is, how can you publish the second app in the App Store which can't be used alone?