Gonna make brief comments on the discussion points. Here goes!
Charizard X: A+ > S: 100% agree with this. Charizard X is just so threatening in the metagame atm. There isn't much I can say that hasn't been said already aside from lure moves making it godly.
Mega Venusaur: A > A+: Once again, I 100% agree with this. It is severely underrated atm, and its ability to check so much of the metagame (including special M-Altaria) - about as much as it did in XY, in fact - just means that there is little reason for it not to move up at this point.
Amoonguss: B > B-: Disagree here. While it is impossible to deny that stall isn't used as much atm, I think before we make any rash decisions regarding stall 'mons like Amoonguss and Quagsire, we need to let the post Lando meta settle down, as a big contributor to stall's decline was Lando. Don't make any decisions regarding this atm. However, if I had to state my opinion ATM, I'm inclined for it to not move down anyway simply due to the great utility it provides over M-Venu (also Regen being the best defensive ability in the game if you ignore Wonder Guard) and due to its great pivoting ability.
Chesnaught: B > B-: Chesnaught is not as good as it was in early ORAS, sure. However, I am on the fence about whether it should move down. Bulletproof is just such great utility for a defensive Pokemon, allowing it to completely wall M-Venu and, with a little prediction, pivot through Gengar (unless they are one of those crappy Sludge Bomb variants that u don't need to predict against lol). It just acts as such a good check for physical attackers, although its weakness to Azumarill's Play Rough is kind of a bummer due to it being a Grass-type v.s. Azu's water. I'll abstain on this.
Quagsire: B > B-: See: Amoonguss.
Scolipede: B > B+: Agreed. I am having a lot of fun using this as a Spikes lead with Protect, Spikes, Toxic Spikes and Endeavor/Baton Pass, and it is just really good atm. Sure there are the offensive and BP variants as well, but neither of them are as fun to use as Spikes. Admittedly, Spikes is set up on by anything with Sub, but you should only really be using it on teams with Electric-type coverage to hit the Sub user that takes advantage of it the best (Gyarados) anyway and it can alleviate the issue a little with Baton Pass anyway. All in all, I agree with this.
Reuniclus: B> B+: Agreed. I left my thoughts on this a few pages ago, so I won't say it again.
Mandibuzz: B- > C+: Agreed. It's niche is not as useful as it was in XY, and its defensive stats are somewhat lacking tbh. If the Aegi suspect had gone the other way (thank god it didn't) I would have been inclined to disagree with this, but it didn't so... really there isn't much to say because, like Rotom-W, this is more of a gut instinct for me.
Kabutops: B+ > B: Disagree here. Kabu is a scary Swift Swimmer (and the only viable physical one). Rain is terrifying in the meta ATM, and if you are building a rain team Kabu is almost a must due to it being the best form of fully physical offense that isn't acting as a pivot in the playstyle. And no: Mixdra doesn't count as physical because it is MIXED.
Those are my thoughts. They aren't in much detail because I'm lazy and not as passionate about these moves as some others, but hopefully they will suffice.
Also
AM what happened to Rotom-W? It was almost unanimously agreed that it should go to A-, yet no movement.
edit: ok apparently Nidoqueen has been nommed, so I'm going to say that I agree with it. Once again, I'm lazy so not much detail, but it is significantly more usable now that Lando is gone, and it acts as a nice bulky attacker that can lay Stealth Rock and/or Toxic Spikes. STAB Sheer Force Sludge Wave and Earth Power are nothing to scoff at, and its access to good coverage options in Fire Blast and Ice Beam if it opts not to run one of Toxic Spikes or Stealth Rock are just the icing on the cake.
Edit 2: Gonna nom
Manaphy to S on the basis that it is about as good overall as Charizard-X is (albeit not in the same role) and IMO if one moves up the other should tbh. Not much else to say here tbh as this is more of a thing that I feel is reliant on something else moving up at the same time to move up. Basically, what I am saying is
if Char-X moves up, move Manaphy up, but if Char-X doesn't move up, don't move Manaphy up. Just a bit of food for thought tbh.