Just MHO, but if one of the features planned for the rewrite were some sort of plugin system or the like (a'la wordpress), I think that could take a lot of the pressure off you and put it more onto the userbase to develop addtl features. As long as the hooks were in place, we could get our geek on and hopefully develop things that some people want, but others don't need (eg: lightbox, exif/iptc, etc).
That said, I completely understand how software can be one's baby and very personal, so i'd understand if you *aren't* aiming for that at all
Either way, i'm still excited for whatever changes you intend to make, and subalbums will be fantastico for many, many folks (I know for sure me). Kudos to tris and everyone else who has helped to this point in development