What if tower damage ignored all base armor
That's...kind of awkward given the general dynamic of champions in LoL.
Concerning the kill-based archetypes in Fighters, Assassins, Marksman, and Mages: champions survive long enough to do their job (killing things) through some mix of defense, mobility, and range.
In regards to mobility
: most of these champions are quite adept at diving under a tower, unloading their full QWER combo in less then 1 second, and dashing out of range while only taking 1 turret shot.
In regards to range:
: a wide range of the champions are quite adept at killing an opponent hidding under their tower without taking any turret shots at all, either from harassing them in the front half of the tower's radius and finishing them off with a long-range skill or flat out having so much range it's a full QWER out of range.
With tanky champions:
: you have to be able to take tower shots to bring much kill pressure.
As buttery as tower defenses are right now, they still pack enough of a punch you have to think twice diving underneath them as a wide range of tanks and tanky DPS champions.
Combined with the existing 30% armor penetration and stacking damage from warm-up and heated up, I don't see adding more anti-defense mechanics on towers as improving the game.