One thing that is different from docker however, is that we generally
want translations/locales in the runtime. But these are pretty large,
so we want to handle them in a smart way. xdg-app has a feature that
allows splitting a runtime into a base and a set of optional
extensions that are mounted in the sandbox only when they are
installed. I use this in the gnome runtime to split out each
locale. Unfortunately Fedora uses a single large locale-archive file
for its locales, so its hard to do that. This needs some research to
figure out how to do properly.

Fedora Internationalization team working with Glibc to split locale-archive. This is in plan as a change proposal for F23.
Hopefully we will see good progress soon.
Pravin Satpute