Skins can have multiple fontsets defined in their Font.xml file. In some cases, you may have the same fonts defined in each fontset (such as symbol fonts or music lyric fonts for the VideoLyrics mod at http://forum.kodi.tv/showthread.php?tid=302448). This creates a lot of duplication and makes fonts difficult to maintain. It would be great if fonts could be defined once in an includes file and then added to each fontset via an include.
Anyone else interested in this, or is this a niche request? 
Cheers!