I’d love to see some story progression in the old starting zones. They are still a favourite to me when it comes to levelling. (And, BfA Kul Tiras is also awesome.) Some of the zones have been devastated by the Cataclysm, some rebuilding would be great. And, a dispersed plague and restoration in the Plaguelands. A re-built dam in Loch Modan and a thriving lake for fishing and picnic again. Darkshore returning as a questing hub.
As for updated graphics, I would be happy with just HD models. Like for example the old Darkshore vs. the new BfA Darkshore models.