Yep - I've already looked into that for this branch but hit snags with grunt spritesmith and the contributions needed to add the configuration necessary to improve the output were rejected by the author. Despite that, I'm still up for doing this, just I was hoping to make it super easy to regenerate the sprite and css if we add regions so we just need to pick a better tool.

Another issue is dealing with 2x images. In which case you either have 2 sprites or use background-size and if you do the latter you need percentages not px based sizing. 

So all in all I think that'll be a follow-up to this rather than part of this.