Suppose a user wants to take advantage of this feature, but they have already installed a lot of ports. How will they do that? After having indicated their preferred locale, would they then have to deactivate and reactivate all affected ports, which would then prune the unwanted locales? How would the user determine which ports are affected? Or would the user have to deactivate and reactivate all ports?
Suppose a user has taken advantage of this feature, and now wants to stop using it. How do they get back the other locales? Same questions again. Do they have to deactivate and reactivate all ports?
I am not wild about this proposal because it is contrary to the principle we've used in MacPorts so far, which is that each port provides a complete set of files and features, even if not every user will use every file or feature. For example, we don't declare variants for every possible configure option; we make a best guess as to the features that would be helpful for most users, then provide variants for esoteric features that would require lots of extra disk space or dependencies. I worry that you will expand your request to add features for removing other aspects of ports that you personally don't need.
There are existing Mac apps, outside of MacPorts, that help you reclaim disk space by deleting unwanted translations, architectures, etc. You could probably use those apps to prune the files installed by MacPorts. I'm not convinced we need to duplicate this feature in MacPorts.
