It would be great if you could get rid of the alerts. I scanned the code but couldn't find where they're generated. A non-modal info panel would be better. Especially the "No songs left to add" one.

I am sorry, I stopped developing this script

If you would like to change it yourself, you probably need to look in the library file:
https://github.com/cvzi/bcplayer/blob/master/BCPlayerLib.js

I am planing to add similar features to Bandcamp script (Deluxe Edition)