I like this idea. The visual speaks too, not a bad in-car mood lighting at all in fact, thanks for putting this up (easy to understand!).
The color & brightness can be independent from the skybreaker and a software option (checkbox) can be labelled "synchronize color" so to have the same color for both footwell and skybreaker. The brightness can (and should) remain independent though.
So... SPI1(SkyBreaker) and SPI2(Footwell) with a color sync option. I'll see if I can wire & write this up. The only challenge now is to think of some ways to have 3 LED per each side enclosed in some type of enclosure that can be discretely mounted somewhere in there. Let me think of something... I'll update on the progress