Would be nice if they dipped outside of PHB a little bit more for some extra spells and subclasses.

If I were to suggest subclasses:

Barbarian - Ancestral Guardian
Bard - College of Eloquence
Cleric - Death Domain mostly because I tend to always play Death Domain (But given the story probably not the most fitting), Twilight Domain could be good.
Druid - Circle of Stars
Fighter - Rune Knight
Monk - Way of the Drunken Master could be interesting (Especially since there are items in the game that directly benefit being drunk which currently have little use)
Paladin - Oath of the Crown
Ranger - Fey Wanderer
Thief - Swashbuckler
Sorcerer - Aberrant Mind
Warlock - Fathomless
Wizard - Bladesinger

Artificer class would be cool as well. I'd imagine there could be some interesting dialogue options with various characters to boot.

A bunch of new magic items would be nice too. Even more so if they backed up some builds made more viable by the new subclasses and spells (Like, better Acid support with some Acid spells for Acid Sorcerer)