(my english is bad, I use Google)
*the idea is that the thumbnail browser load a specific autoplaylist (thumbnail browser its that vertical bar with small covers)
*Imagine a playlist that shows most played songs by you. (Kind Top 50 Most played)
*Imagine also that the thumbnail browser, now shows something that already is in the player, What you see in main panel its the same in thumbnail browser
Remove thumbnail browser and all covers is taking the beauty of a resource that was created perfectly, unique, something that make this player better than others.
I'm not sure we're on the same page here.
My suggestion is mainly to completely remove the album art from the expanded panel, and simply highlighting the concerning album by dimming all other album arts in view.
This would give more space for more info about the specific album. Such as maybe genre, musicians, custom tags, etc. etc.
Maybe we agree about something here, but I think I probably don't understand your remarks on Billboard and autolists.