I might be losing my mind, but I could have sworn I had a conversation with you a couple of years back (maybe on the old iSubapp.com forum?), about how you'd built iSub specifically to pair with MusicCabinet! The website is here, in case it refreshes your memory:
http://dilerium.se/musiccabinet/ - I can also PM you an account to my server if you want to see it in the wild.
At any rate, MusicCabinet is a really lovely mod, based (I believe) on Subsonic 4.6. It's tag-based, rather than folder-based, and it does really cool things with the Last.fm API. Unfortunately, it's been abandoned by its developer, so people have been drifting away from it over the last year or two. But I just love it too much to give it up until I have to. It works beautifully with iSub currently (I've used them together every day for the last several years).
I was just curious as to whether the updates you have in the pipeline would be what finally pushes it into obsolescence for me. I guess I'll have to wait and find out!