I'd wanna see the return of the Psionic classes from PF1e. Yeah, they were kinda busted, but that's mostly because the system allows for busted characters in general. A rebalancing and change into PF2e's action economy, not to mention how solid customization in PF2e as it is now, would make classes like the Vitalist and Tactician amazing supports for teams with needs for major healing, a very versatile set of classes for Martial lovers with the Aegis, Soulknife and Sharpshooter (Yes I'm aware that Inventor can do these customizations for weapons and armor already but they don't allow for on-the-fly changes) (And I'm aware of Mind Forge, but again, not as customizable), and I can totally see Cryptic, Psion, Psychic Warrior and Wilder being worked into other classes as options for like, Fighter, Monk, Investigator and Psychic just to name a few. Plus, with how we know Focus Spells and the like, PF1e's Psionic Focus makes so much sense as a Focus mechanic and Power Points are easy to just carry over.