I am not even sure there is a Google API that would make this possible, but:
I am a heavy user of Google Music. It would be nice if there was a way to merge my Google account's track ratings and play-count for tracks into gmusicbrowser.
I don't know if there is an API and I don't think google music is available in europe
But most importantly, I've got lots of higher priority plans for gmb, so maybe one day, but not now.