Clinchfield was the first DLC to ever get Mastery outside of a base game route, but that means that you could just add Mastery to Perserved Collection routes - especially MSB, NTP, LIRR and GWE which already have rewards made - or even create new Mastery content! Would also be a great reason to add scenery additions to updates wich are long overdue or coming (PIS updates) anways.
