In lieu of other threads (there have been Seaside and Alchemy threads)
Prosperity: Replace Loan, Talisman, Royal Seal, Expand, Goons (but give one of the replacement cards its below the line effect), maybe Counting House (it's great when the card works, but that's not often enough, and that wasn't enough to save Coppersmith), maybe Monument now Plunder exists (but it's probably fine). A good reason to replace the cards would be to open up slots for more VP token ideas.
Cornucopia: Probably fine, although if Navigator gets replaced then maybe Harvest could pick up the slack (Reveal the top 5 cards of your deck. +$1 for each differently named card. Either discard them or put them all back)
Hinterlands: Replace Cache and Ill Gotten Gains with Events, and with Events now in the set they can fill in the Blanks. Replace Duchess, but give its below the line effect to a replacement card/event; one that can genuinely incentivise buying Duchies early in certain kingdoms instead of being a "sure why not". Replace Develop. Margrave and Oracle are ok but Margrave's attack is too strong for its vanilla effect to be Smithy with a bonus, and Oracle's attack is a bad combination of weak and annoying, so maybe those cards can be retooled.
Dark Ages: Replace Rebuild. Cultist would be worth a look as well as too overcentralising and not in an interesting or fun way (but it's probably fine). Vagrant is a "why not" card, and I think Donald X has gotten better at designing those sorts of cards (Ratcatcher and Patrician/Emporium), but it's not as bad as Pearl Diver. I'd prefer if Fortress had "When you gain or trash this, if it's your buy phase, put it on top of your deck, otherwise, put it in your hand" to make it useful in more games, or if Rats let you trash a hand of all Rats, but those would be controversial.
Guilds: Masterpiece could be an event. Events seem like they'd work really well with Coin Tokens and/or overpay. Rereleasing it with Masterpiece replaced with an Event and 17 new events would be a good replacement.
Adventures: One of the best things about the rereleases is the fact that blanks get filled in. Between now and the time for a rerelease, Donald X et al could come up with ideas for 6 more events, and maybe by then cards would look like they need to go (although as of now my only issue is Gear BM seems a bit too good)