1 - More things to spend gold on! After about tier 2 at maximum, money just kind of becomes meaningless. As the bastion system has already been mentioned, I suspect my wish has been granted here.
B. Better creature statblocks. 5e usually comes down to both sides hitting each other for a while until one side is dead. It would be good if the monsters could do more things.
(iii) More classes. Not in the PHB, but added slowly over time. Artificer, warlord, psion/mystic, swordmage, and summoner/pet class are the ones I'd want to see. Some in setting guides, others in xanathar's style books. I wouldn't object to Blood Hunter coming in a Wildmount book, but I don't think that class is 'needed' either.