Be able to reuse / extend an icon theme's mapping

Font Awesome 5 provides multiple way to use the Icon set, as web font, as svg files, as svg sprites, as svg js, etc. My use case came from the desire to reuse the mapping and just change the render calls.

But since IconThemes content are not rendered I was not able to do something like:

{{include reference="IconThemes.FontAwesome.Mapping" /}}

Rendering the content of an IconTheme might have some performance penalties and might not be necessary.

Still it would be great to be able to reuse the mappings, inherited it somehow.
Maybe we could have something like

xwiki.iconset.inherit.mapping=IconThemes.FontAwesome

and be able to provide just the differences.