Been a bit busier than planned, sorry! I thought of fiddling with the XML myself, but haven't had time to make sense of it yet.
Mostly I would say fewer gradients, except maybe the library explorer header and background for Track Details tabs, and make the left panel all one color (no backgrounds on the major nodes). Oh, and make the sidebar/compact player purple, along with MusicBee button and windows buttons in corner.
Thanks again for your help on this!