From the perspective of RMFRP and varied settings / house rules, I'd find this quite useful. As I like alternating my settings so tend to change it from time to time (having run games in Privateers, Shades of Darkness, Dark Space, Shadow World, and Middle Earth, and some homebrew as well even if not lately), it would be handy that I could keep the setting-exclusive skills in their own files and only put them in the ERA directory (of a given game) when I need them.
Currently I instead keep a massive master skills file and try to curb it when I need to make a setting-specific skills list. For the first few iterations, I'd easily end up with a few extra skills that should not be in the setting-specific list.
A note however: if some skills came from various Companion books, I'd like those files to be editable. ERA expansions tend to be in un-editable format, so, changing e.g. a race or a culture means I have to entirely recreate it as its own race or culture file*. If this happened to skills, too, that would have the added inconvenience of not being able to remove the skills that I'm not using, so they would uselessly stick around on the character sheets.
* I recently noticed that the professions can be edit-overwritten using the new variant profession feature, that's rather cool and convenient!