Add a way to specify applications to be installed in UI meta packages without making them depend on it

One of the things that really bothers me in Android is that I can't uninstall default apps to replace them with alternatives, the best thing I can often do is disabling them but they're still installed.

Right now this is the same on postmarketOS: the packages that come with the UI meta packages can't be uninstalled without uninstalling the whole UI meta package. Basically we're abusing the $depends variable which specifies dependencies required at runtime for the package to work, but for UI meta packages this is not the case.

I'd like to be able to specify in UI meta packages what applications to install by default so they are added to @world, but not having the meta package depend on them. Preferably this would be some upstream variable (there have been discussions of "recommended" or "optional" deps before in the Alpine devel mailing list but nothing came of it so far), but for now this could probably be done with pmbootstrap? Maybe a new variable which is only valid in UI meta packages, $_depends_recommended (or something), in which we will specify the default applications so pmbootstrap can install them, add them to @world, and that's it?