I'm going to be mildly disappointed if Baldurian background is forced on custom characters too. I want to make my own character have a Waterdhavian background. As I am taking part in a tabletop campaign that's centered around Waterdeep (specifically Dungeon of the Mad Mage), I am privy to certain plot points already present in BG3 that would be interesting to explore from that kind of background.
Namely, the Zhentarim and Mindflayers have a HUGE presence around Waterdeep. Other than Gale being from Waterdeep himself.
Also Waterdeep is much bigger (Population 1 million) than Baldur's Gate (Population 42,000) and far more fashionable, richer, more influential and cosmopolitan. You are essentially outclassing anyone from Baldur's Gate.
Nothing against Baldur's Gate of course, I think its the far easier jumping off point for adventures than Waterdeep would be. Has anyone even simmed Waterdeep anyway?