I want 160gb classic back!
We're about at the point where I think a 256GB flash-based iPod would be economical, especially with cheaper/slower flash (doesn't really need to be very fast for this use case). It would provide capacity and still have no moving parts, checking all the boxes for me.
"I know I don't listen to half my music. The problem is, I don't know which half."
The last thing I want to do is shuffle albums/tracks between lists that keep track of which items I listen to, and which ones I don't. And it changes over time, too. That would probably be several days' worth of work. Far, far, far cheaper just to buy a larger device.