Want to focus on the A- and B+ rank only for this post:
I don't think anything should be dropped from A to A-. While there could be made a case for Gliscor or Mew, they are both huge threats to defensive cores (not only stall but heatran / ferro / chomp stuff too) with both Taunt sets and SD sets (for Gliscor) Mew is really solid in A for me because it is also amazing against offensive teams, being able to check pokemon like MMedicham, MMetagross and non Specs Keldeo and with great options to support the team with Defog, Taunt, Heal Bell, Baton Pass etc. Gliscor is a bit less worthy of A, but I don't see a reason to drop it because it's really hard to take down without a strong ice or water move and it doesn't give too many free switchins to other pokemon because it has access to Taunt, U-Turn, Toxic and Knock Off.
Alakazam was nominated to drop but the pressure it can put on balanced teams with a LO 3 Attacks + Taunt / Encore set is huge. kek123
The special walls you mentioned in Clefable and Skarmory are both not the best switchins for Alakazam because they are both forced to Roost / Soft-Boiled when hit by Psychic / Focus Blast, so they will just be Encore bait. It's not easy to pursuit trap because Tyranitar gets outsped and ohko'd by focus blast even with a scarf so 70% of the time that means r.i.p. tyranitar. Bisharp is in a 50/50 anyway and when you face Sub Alakazam things are even getting more complicated. Krookodile is also OHKOd by Focus Blast and with a scarf a OHKO is not even guaranteed if Alakazam decides to stay in. The only Pursuit trappers that are left are Mega Aerodactyl, Weavile and Scizor and I think it's pretty obvious that they have some huge flaws when they click Pursuit or even when they have it on their set in the first place (less coverage for weav / aero, choice locked for scizor)
Celebi was nominated to B+ a few times but apparently the council doesn't agree with it so I won't start this discussion again. Just want to know what the thoughts are on Celebi atm.
Jirachi has been nominated to go A a few weeks ago and I can only agree with this. It's one of the best switchins to pokemon like Gardevoir, Latios, Clefable, Alakazam.. without being worn down extremely quickly because it has access to Wish. Steel types are extremely good rn and SpD Jirachi has the cool niche in not being trapped by Scarf Magnezone (even without Protect you lose a max of 1,3% if you spam Iron Head + Wish so you only lose if you get really unlucky with getting paralyzed + getting fully paralyzed a few times in a row)
I don't know why Serperior isn't in A at the moment. The usage of counters / hard checks like tran and torn-t hurts, but it can both cripple or lure them in and even if it just uses the standard HP Fire Miracle Seed / LO set, it is still an amazing offensive check to offensive water types and many passive pokemon like hippowdon and ferrothorn. The unpredictability in its moves bar the obvious Leaf Storm with moves like Taunt, Glare, HP Rock and Sub, make it really hard for pretty much every team to check.
Latias to A- sounds okay. Outside of the extra bulk which barely comes to play, it only has a niche in Healing Wish over Latios. Since Starmie is now in A- (and I don't think Latias is better than Starmie in this metagame) I think Latias should join Starmie and go A- too.
Dragalge should drop too (B+ > B) Bludz made a good post about this so instead of posting the same arguments in a slightly different structure I'll just link the pots here
I also think Victini should go from B+ to B. Yeah it can lure in pokemon like Hippowdon, Heatran and Garchomp really well, it still requires a lot of team support. I'll use Garchomp as my prime example here because the tank set only gets around 20-25% usage. First of all, Victini can't just spam V-Create, because it both loses 28% of its health and Garchomp gets up rocks freely. Rapid Spin and Defog exists but most hazards removers have terrible defensive synergy with Victini. Psychic types like Starmie and Latias stack up 3 weaknesses and make the Pursuit weakness even bigger (and I think the Pursuit weakness is a really big argument in the case of Victini because of its lower base speed and V-Create drops) While Alakazam avoids being trapped by Tyranitar and Bisharp to an extent, Victini is trapped by both of them. Even without scarf, Tyranitar will be able to trap Victini after a V-Create drop so that's even worse. About Garchomp, even when you make a prediction and lure it in with Icy Wind, you only do around 55% max to 76 SpD Tankchomps and you are still pressured a lot later in the game because even a banded V-Create fails to KO a Garchomp after it took a Icy Wind before. Other counters / hard checks like Suicune, Bulky Zard X and Scarftar are also way more common than at the point where it was moved to B+. I think B is fitting more than B+ looking at the flaws I described.
Stay: Alakazam, Gliscor
Drop: Victini, Dragalge, Latias
Go Up: Jirachi, Serperior