Like, hear me out. No one likes dealing with Cait and her critting headshots, Jinx and her passive + Rocket Crits, Trynd and his RNG crit chance, and Yas' crit chance doubler. Its just not fun and not fair to really fight against unless you can have the same feats, which if we are keeping to originality, no one else really has anything that matches them. The only champ that doesn't have stuff like this that tries to use crit to their advantage if regular standard builds fail is Riven, due to her passive gaining tons of power from this stat increasing rune system (aka Conq giving AD per stack, Trans giving AD per 1% extra CDR, Gathering giving AD per 10 minutes, etc) paired with her R1. Crit got nerfed into the dumpster (then resurrected) because it made ADCs the best at damage period, making everyone second dog to them.
My idea is that instead of doubling your auto's damage, it increases your auto's damage based on how much crit you have. The calculation of the auto damage is where it gets tricky. I don't want ADCs doing 0 damage to tanks, but at the same time I don't want them to punch through tanks with ease. The middle ground is what im trying to figure out.
Numbers and items would have to be tuned, but a rough estimate on how that would work could be something like this:
Standard Build is IE + 2 crit items. What those two crit items are is up to the user to build per the situation.
10% crit = 10% increased auto damage
IE's passive would give up to 40% extra crit (gained by having two other complete crit items)
Crit items give 20% crit max. glove still give 10%.
AS crit items will gain 20 AD on completion (Zeal is 10) (just like how Tri gives 5% ms on completion).
(These are not exact, they do require tuning so ADCs avoid getting shafted too hard like what Riot did previously)
This way, it makes it fair to ADCs and other crit users to not pray to RNJesus for a crit till they max out crit, but at the same time doesn't make crit super strong. Making it a 3 item core allows the users to be able to grab two non crit items for the situation instead of being shelved to one. AD stat growths on ADCs may or may not have to get upped.
At the same time, it alleviates the headache of being unable to really mitigate crit damage (omen does a bit of work, but is easily nullified by a LW or BC), as the users who make the most out of it (Cait, Trynd, Yas, Jinx) will be given adjustments and changes around it. This does mean ADCs might have to build a LW to deal with tanks, but at least they can build another damage item with it instead of that filling the last build slot (which made crit have to be strong). The possibly of more unique and different builds would exist, but i'd leave that to the community to explore. This change does open up crit to more users than just ADCs at the same time, making it a general stat instead of a mainly ADC centered stat.
EDIT: Its to also prevent ADCs from becoming Judge, Jury, and Executioner like they were during the "Tank" meta. They are slowly creeping on it, and all it takes is one or two changes. So what if the first "20-25 minutes" is decided by mid top and jg? Its not just because your lane is the weakest, therefore they camp it, its because you are also the strongest lane at the same time, dictating the result of the game. This is the very meta that existed with tank meta, yet who was it that got blamed for it? Oh thats right, tanks.