AD Armor Item Idea
I'd like to suggest Armor item that is oriented for AD champions - skirmishers, fighters and tanks, that is focused on defensive scaling
Warrior's Crossguard 40 Armor 40 Attack Damage 20% Attack Speed 10% Cooldown Reduction Passive: Increase your armor by 5% (3% for ranged) per basic attack or per ability cast that damages enemy champions up to 30% increased armor for 8 sec. At max stacks you gain Edge of Survival: Each second while damaging enemy champions you restore health equals to 2% of your missing health + 10% AD
The item originally was made to benefit melee auto attack fighters.
Such champions are 
Master Yi, 
Xin Zhao, 
Olaf, 
Tryndamere and so on
Those fighters rely on their basic attacks to get the job done and it requires them to stick to their target for longer period of time, exposing themselves to direct danger so this item would reduce that vulnerability
However there are wider variety of champion that do not care much about attack speed but rely on their abilities to get the job done
Some of them are 
Wukong, 
Jarvan IV and 
Vi
Those warriors rely on their abilities for most of the part and cooldown reduction and scaling armor would benefit them quite a lot especially if they decide to increase their tankiness further which will extend their duration in teamfights.
Some of the tanks are 
Garen, 
Renekton and 
Poppy
They don't care that much about how much damage they do but extra cooldown reduction and scaling armor that gets better by stacking more armor is welcome alot for them especially versus AD opponents. The longer they stay in the fight the stronger the defensive stats becomes and at reaching max stacks will trigger Edge of Survival, granting extra health regeneration, thus will make them even harder to takedown.
Even if the item is oriented for AD Champion but other possible champions are
Malphite and 
Rammus
They are AP champion in general but the item provides scaling armor as well as other ways to benefit them for better endurance in the fight so there might be a chance that the item would benefit them
The item is made for melee champions but range champions might also benefit from it
For example such champions are 
Graves and 
Gnar
They would get the same benefits like melee champions, however for ranged champions is much harder to reach max stacks to trigger Edge of Survival regeneration. Not only that but the item benefits from stacking armor. For marksmen it will make them more tanky but it will reduce their damage output significantly as the item scales in defensive manner rather than offensive.
