I think you're vastly overestimating how many people use a VPN. Dynamic IP is zero problem, your ISP knows who's on what IP at what time (logs of this kept for x months required by law in many countries).

This case is for movies rather than music but ISPs are already ending up having to go to supreme court to fight , I hope more ISPs are prepared to do so https://www.techdirt.com/articles/20180508/06040539799/danis...