* High ground advantage/low ground disadvantage system being replaced by a +2 bonus to AC if an enemy is attacking you from low ground, to act as a replacement for the missing cover system. This makes room for Sharpshooter feat to be implemented without being grossly overpowered (for the uninitiated, it gives +10 damage to ranged weapons at the cost of -5 attack, along with ignoring AC bonuses from partial cover), makes actual spells and abilities that grant advantage more powerful, and also removes the need for backstab advantage.
* Proper reactions being implemented
* Ready actions being implemented
* Dodge action being implemented
* Disengage being its own action and being a standard action/Shove being a standard action (okay, people who have seen my posts would wonder why this is lower on my list of priorities even though I typically put a lot of emphasis into them, but quite frankly the above would have a far bigger effect on expanding tactical variety in this game than Disengage and Shove changes. I would not care if Disengage and Shove remained the same as long as the above happens first.)
Everything else I literally don't care about, because they're either a given or I don't have any particular strong feelings about them (particularly in regards to more races or customization options). Well okay, I want College of Valor Bard and Arcane Archer Fighter archetype, but they're both probably in the 'given' category too. It's pretty obvious I highly favor magical archers at this point, but Rangers with the nature focus literally do not appeal to me at all for some reason.