Comment 6 for bug 1585903

for the record:
My advice is to do the same way we handled optional modules and features:
- have light-themes-gtk2 seeded by default
- relax (in debian/rules, hack the generated shlib dep) the dep between light-themes-gtk2 to libgtk2 to not be listed
That way, people will have the theme available, and the first application needed GTK2 will fullfil the necessary dep

that's how we handled for a long time having Qt modules with ubuntu's behavior without pulling Qt
yeah, at least, we don't pull our theme for other derivatives.
The other way around (libgtk2 to recommends the ambiance theme) would impact all flavors