As far I known, data/binary format and package format of flatpak are frozen.
Because flatpak is distro agnostic, there’s is sensible to add computer-wide programs/runtime installation path. Many distro could add installer option to select an partition for such installation (also installer could try to autodetect it).
It’s sensible by two reasons:
- User could reinstall/change system and keep any installed program still exist on one’s computer
2, User could power off computer, ran another system and be smile with usage of the same programs