there's already been some suggestions i agree with, throwing in my own few cents
-species to have their mechanical identities strengthened.
-class versatile subclasses (i don't mean prestige classes but i do want those too).
-some sort of martial system to rival the effectiveness of spells.
-this is more of a personal wonk but i'd like it to try removing multiclassing, but with more ways to customize through feats and similar.
-emphasize the different gameplay pillars again and let classes have specific niches within them, not every class needs to be fully combat capable.
-try AEDU again.
-more in-depth weapon/armour systems (more types, materials with different properties, ect)