A serious question to the Champion Designers

Cause AP is a better tool for zone control ?

If you have an AP champion you can put more power in their abilities, since they have no other outlet. AD champions or tanks have their AA damage and tankyness which already contains a big part of their power, resulting in less power for their abilities. Since AP champions are mainly squishy their zone control is their main source of survival whereas AD champions or Tanks have easier sustain.

A marksman's zone of control is their autoattack range. If they've got any items at all, stepping in range without a plan usually leads to a bad time. Caitlyn particularly excels at this depending on her location, since she can set up a wall of traps that block an entire path, and headshot damage HURTS.

Otherwise, the only other AD champions are melee, who can't exert zone control due to being melee and having no threat outside of their AA range and/or their gap-closer. Illaoi is the closest you get - she can't really dash to you, but being in a pre-tentacled area gets you crushed.

If you wanted, say, someone with the kit of a mage, but with all AD ratios, that's a bad idea. Now you have mage-style burst with marksman-style sustained damage. That's a recipe for disaster.

Because they tried that with Gankplank and it turned into the worst worlds final matches of all time.