Moonstone plugin proposed improvements (see attached patch & images)
While working on something else I had to try some changes in the Moonstone plugin to test a proof of concept, which were successful, btw. The POC involved implementing a "shading" option, which if added to Moonstone would bring it's appearance very close to tallica's expressed original concept (see Moonstone plugin original commit image) while retaining the needed playlist subsequently added before release. Therefore I've decided to contribute this work back to you.
This proposal also adds an ability to access the Settings dialog in order to return Audacious back to another interface and an option to exit Audacious. As currently implemented, I know of no other way to change back out of the Moonstone interface without either killing Audacious by brute force and editing the config file to restore back to another interface - OR using the Status Icon plugin and it's menu! If there is a better way of getting out of the Moonstone interface, please enlighten me! There is still at lease one rough edge that I didn't get to investigate after successfully implementing my POC for "something else", namely, adding an icon to the "flat" and "flat dark" themes for "go-top" (the icon for the new "Shade" button, which already has a proper icon in "native" mode resembling an up-arrow pointing at a ceiling).
These proposed changes should make Moonstone a much better and more usable interface option for Audacious. Please see attached patch file.