At least on the Android front, I'd prefer the app allow me to write to my own storage target. The reason is because I already use Syncthing-Fork to monitor a parent Sync directory of stuff (Obsidian, OpenTracks, etc.) and send to my backup system. In effect it allows apps to be local first and potentially even without network access, but allow me to have automatic backups.

If there were something that formalized this a little more, developers could even make their apps in a... Bring Your Own Network... kinda way. Maybe there's already someone doing this?