Fallback GlyphData for Components?

Since I had some issues with the ‘Rebuild Components’ involving the definition of glyphs and components I was wondering if it’s possible and worthwhile to be able to set a fallback component in the GlyphData.xml?

As in, now the GlyphData.xml defines

<GlyphInfo: <0x6000002e8600> N:abreve, U:0103, Sc:latin, Cat:Letter, SubCat:Lowercase production: (null), sort: (null) Components:a brevecomb >

But what if I’m using just ‘a breve’ or even for cap examples ‘A breve.cap’? I can of course change my glyph data but then I have to have separate files for every typeface I work on?

It would be good to be able to set components ‘a (brevecomb, breve)’ so that if one is not available, it takes the next one?

There where a few places where I though about adding alternate decompositions. But I wasn’t useful enough to actually implement it.
There will be some font file that only have the spacing glyphs but that will only be temporary as I only recently switched over to only use the nonspacing accents.

The .cap accents don’t need to be mentioned in the glyphData file. On composition, it will look for glyphs with a .cap and .case suffix and will use that glyph as a component.