Touchgram is a free message creation app that lets people create interactive messages inside Apple iMessage. It has complete privacy with no knowledge about users. Depending on message size, most are sent via cloud storage (anything with one or more photos or sound recordings).
Problem - if you don't know who's using the app, how can you offer to keep their data in-transit inside their country?
Idea - offer a subscription service so users can specify their choice of data centre.
Buying a subscription keeps it anonymous - the choice of centre is still only stored on that device. We don't know who bought subscriptions - Apple just provide the token on the device to enable the feature.
Does this seem like an attempt to gouge people?
Would this make you worry more about the privacy of data being sent via the app?
I think you are wildly over estimating the care that people place on their data.
I doubt anyone except hardcore techies would pay for that.