Now, I see that Charizard-Y is an A-rank so far, but I honestly do not agree to that.
My reasoning is: With Drought it becomes a terrifying wallbreaking sweeper, to put it in a strange way, which is incredibly hard to deal with. It has the exact tools it needs to break any would-be counter aside from the blobs that it is very hard switch in on. Basically, you have to sacc something or let anything take a huge hit for a chance to revenge kill this beast. And even then, it sports a pretty good 78/78/115 defenses which means if it has to, it can take a hit. It can also support it's team with the aforementioned ability in several ways: The most obvious one being that it empowers fire-type moves. But there's also the defensive factor in it, as for instance you're at the end of the game and a banded Azumarill threatens your remaining pokemon, which are all weak to it, with it's very powerful Aqua Jet. You can easily sacc it simply to abuse the defensive boost from the sun and score the win instead of falling out on a loss. And that is a gimmick few other offensive pokemon holds. And, I'm actually using this as an example, as this is exactly what's happened to me.
As for how it holds up against it's A companions, it 2HKOs all of them aside from Chansey with his incredible special moves, meaning you're forced to sacc and revenge the threat. And due to him sitting at a comfortable 100 base speed, he's still capable of finishing off whatever mon that are to come in.
In regards on how he holds up to the current S-ranks...
He will win 1v1 against unboosted Physical MLuke. As far as experience goes, MLuke actually finds setting up SDs a bit of a chore, so this is an option. He will win against +2 Special MLuke. He can switch in on the Nasty Plot and plummet the threat away with a Fire Blast or Flamethrower.
He destroys Aegislash. He is one of the mons that OHKOs straight from the bat.
Specially Defensive Mega Venusaur is 2HKOd by Fire Blast and has a MinMax thing on Flamethrower. Obviously, if he switches in on megavenu, the saur can easily synthesis stall him out of Fire Blast pp if need be, but flamethrower is still a very competent option and MegaVenu will lose out in the long run. Also, as mentioned, MegazardY can setup a sub on the Sleep Powder, making him all the more deadlier.
He scares out Genesects that lack Tbolt, and if the Genesect does have Tbolt it won't kill. It's more situational, but very convenient for this mon.
Deoxys-S cannot OHKO even with specs TBolt, if you're into that shit. But Deo-s still reliably sets up hazards on him. Sub is broken by Psycho Boost, so he cannot set up that on it either.
It also forces many switches, granting it free opportunities to either go for an insanely powerful Fire Blast or set up a sub. A ZardY behind a sub is most definitely the one thing I'm most afraid off when I see one on the opponent's team.
It can also run a very effective mix set, which still hits incredibly hard and means that Chansey is no longer an issue beyond heavy recoil. It works similar to the mix MegazardX set, just with more immediate power on both sides. The Flare Blitzes from both unboosted are, well, not that far from eachothers. Of course, the other physical moves will stand weaker, but the mons that check ZardY has now dropped.
252 Atk Mega Charizard Y Flare Blitz vs. 252 HP / 0- Def Abomasnow in Sun: 1428-1680 (371.8 - 437.5%) -- guaranteed OHKO
252 Atk Tough Claws Mega Charizard X Flare Blitz vs. 252 HP / 0- Def Abomasnow: 1440-1696 (375 - 441.6%) -- guaranteed OHKO
Of course, this thing is a nuke, but if there's something he wish he had, it'd be a better speed tier. 100 isn't the greatest speed for a sweeper, but seeing as this guy is more of a wallbreaker and a supporter for a team member, I'd say the speed isn't too worrisome. At the very least it does not conflict with his role as an absolute destructive wallbreaker, as no wall runs max Speed. So, yeah, being capable of 2HKOing everything, EVERYTHING, in OU but Goodra, Chansey and Blissey after Stealth Rock should be a good way to underline his wallbreaking power.
So, all things considered I'd say he is A+. I'm willing to hear any rebuttals of course. Also, I didn't take stealth rocks into consideration anywhere in this post, so it's somewhat theorymon at that part. Mainly because it's obvious on how it affects the pseudo-Dragon.
Edit: Damn, this post looked smaller when I wrote it down. This is a crime to my laziness, I tell ya.