Pathfinder 2.0 looks like it could give us a great opportunity to expand the playstyles of all of the classes in a variety of ways. One of the ways I'm most interested in seeing this take place is making viable lightly armored dex builds, heavily armored strength builds for all classes be viable from the beginning and to feel different in how they play.
I'm not going to get into the dex to damage thing here, that's it's own can of worms. This is all about armor and being able to make something like a lightly armored fencer paladin or a heavily armored battlemage from the get go, without being locked into a specific archetype or feeling like you're giving up important class features to get it.
Something along the lines of heavy armor giving some light damage reduction and a bonus against effects that attempt to bodily move you like combat maneuvers while light armor has more mobility, better touch AC, possibly some sort of dodge action/reaction similar to how the new shield mechanic works.
Being unable to make a shirtless tattooed barbarian who uses their con to absorb attacks without one specific archetype or when I multiclass into monk to play an unarmored warrior but because the scaling AC bonus doesn't continue with multiclass they would become less and less viable over time was also an issue for me in PF1, and something that seems like it would be easier to fix in the base system rather than relegate them to specific archetype.