I'm thinking about updating an app and adding In-App Purchases for some of it's existing features. At the moment it's completely free so this would definitely cause a few unhappy users and negative reviews.
The app has some files on the device, so i could check which users are new and which ones are just updating. Based on that i could keep everything free for those who have it installed at the moment.
Is is possible to give away In-App Purchases for free, so those people could get the same "status" as new customers?
What do you think about this method? Would i still get bad reactions? Would this be ok with Google? Do you know a better approach?
The current users if they reinstall the application then those files will be lost and they will have to pay to recover the lost features.
What i think you could do is that you launch a intermediate release in which it is explained that they must register to enjoy the features in the future.
But this implies making a registration system, if it is not very large it could be done using Firebase, then in next release with in-app-purchases they could no longer register but they could recover the characteristics with their registration data.
To avoid that someone with the intermediate version can still register after the release with in-app-purchases you can put the registration table (or collection) in Firebase in read-only mode just at the point of the new release.