Well I'm on the council here, so I'll go ahead and make a post expressing my opinion on all of these.
Fast Pivot Mienfoo A -> A+
Agree
Elec. explained this one very nicely. FastFoo exchanges the ability to take some hits in order to check things like Onix and Pawniard more reliably. I was torn on this one for a while if I'm honest, since I've found myself in so many situations where I removed my FastFoo for a SlowFoo; I often value the ability to SlowTurn more then the incredibly reliable Pawn check, though this has a lot to do with the way I build. As such, I can see FastFoo's strengths, and even though I rarely use them and see it as mostly outclassed by SlowFoo, it should rise, as it can definitely pull its weight on teams.
Defensive Rapid Spin Staryu A+ -> S
Disagree
For those of you who know my playstyle, this might seem weird. As a player, I generally like to use either really defensive Pokemon like Spritzee and Ferroseed, or really offensive Pokemon like Carvanha and LO Pawniard. As such, it might seem like I'd be able to appreciate defensive Staryu's ability to function as a bulky Water-type while providing my team with hazard removal. And I used to do so. However, recently I've strayed away from this set and gone to the offensive Eviolite set as my hazard removal in stead. And it's been working wonders. Thanks to the Eviolite, the offensive set still has the bulk I need, while being much more threatening and much harder to spinblock. As such, I think the defensive set is outclassed by the offensive set and thus shouldn't rise.
Z-Mirror Move Vullaby A- -> B+
Disagree
This one is a very hard one for me. On one hand, I've used ZMM Vull with great success and think it's an incredible sweeper with great power. On the other hand, it faces extremely heavy competition from NP Vull, which is much more splashable, has better coverage options (Hidden Power, Heat Wave vs Rock Smash), and the ability to hold an item that's not Flynium Z. However, ZMM has the huge advantage of being able to be threatening on the turn it sets up, while also having more powerful moves (Knock Off > Dark Pulse, BB > Air Slash). After thinking about this one a lot, I decided to take a careful look at the rankings here, and saw that Scarf Vull is B+. I 100% think ZMM > Scarf, and since NP is already A+, thus two subtiers above ZMM, the fact that NP > ZMM is made clear already, so ZMM is fine where it is.
Magnet Pull Magnemite B+ -> B
Agree
Elec. already touched upon the fact that Magnemite can really only reliably trap one Steel, being Ferroseed. The main thing I want to say is something else though: Magnet Pull Magnemite is pretty much completely outclassed by Diglett. Sure, it might need opposing Mag's Sturdy broken, but so does Magnet Pull Mag. And sure, Diglett needs to play mindgames with Pawniard, but Magnet Pull Mag doesn't stand a chance against it unless it's rocking HP Fighting (Pawn outspeeds, 2HKOes with Knock Off). And sure, Diglett can't trap Ferroseed. But Diglett is a significant threat to all of these, just like Mag is. Both force their opponent to keep their Magnemite's Sturdy intact and keep their Pawniard safe. The main thing Mag has over Diglett is the ability to trap Ferroseed, but Diglett just does so much more. It traps nearly everything. Magnet Pull Magnemite is almost completely outclassed by Diglett and should drop to reflect this, as a B+ ranking is too high for something that only traps Ferroseed.
Choice Scarf Shellder B -> B-
Agree
I don't think I've ever seen a Scarf Shellder do anything useful. A lack of STAB on its main moves just means it's too weak to have a significant impact on a game, no matter how good multi-hit moves are. And with it lacking a good way of hitting bulky Fighting-types and Fight spam becoming more and more popular, Scarf Shellder should drop.
Defensive Cottonee B -> B-
Disagree
I'm going to start this off by saying: yes, defensive Cottonee is bad right now. It doesn't really do a great job of checking anything really, as it is easily worn down and eventually just KOed. However, I do not think it should drop down even lower than it is. Offensive Cottonee nearly completely outclasses this set, but this is already shown with their two subrank difference. Defensive Cottonee is still useful as a way of preventing certain sweepers from setting up, and can still do what the offensive set does to some extent. But the main reason I don't want this to drop: it's better than Z-Nature Power. The most important thing in VRs such as this one is relative strength, and with Z-Nature Power sitting at B-, defensive Cottonee should be B to reflect that it is better. Why I could suggest a drop for Z-Nature Power, I think it's fine like this and we should keep it in B-.
Shell Smash Dwebble B -> B+
Disagree
Fight spam is becoming more popular and it's the worst enemy of a hermit crab with no shell. SS Dwebble struggles too much to break through the very common bulky Fighting-types like Timburr and Mienfoo, as well as bulky Water-types like Staryu, which is also very common right now. The meta is just not at all in the favor of this rock dweller, and as such, it shouldn't rise.
Baton Pass Aipom B- -> C+
Agree
I have a hard time imagining what Baton Pass Aipom is even supposed to do. To me, it just seems completely outclassed by every other Baton Passer due to its frailty and near complete inability to take advantage of its own boosts. I guess there's the surprise factor, but would anyone really use this? I just don't see it happening (also fun fact: BP is not even an other option on the Aipom analysis). Its niche is Nasty Plot passing, but it doesn't do it well and I can honestly see this dropping further.
Choice Scarf Scraggy B -> B-
Disagree
Scarf Scraggy is extremely strong as a late-game cleaner, as a powerful High Jump Kick is incredibly hard to switch into, especially when it's coming from a Pokemon with access to STAB Knock Off as well as Iron Head and Zen Headbutt. In addition, opponents will often fear Scraggy setting up a Dragon Dance, forcing them to make risky plays to prevent this, which might just give Scraggy the Moxie boost it needs to win. So, while it does face competition and it's somewhat outclassed by the Dragon Dance set, Scarf Scraggy manages to take advantage of the existence of that set and is still a solid cleaner, so it shouldn't drop.
Swords Dance Pancham B- -> B
Disagree
My biggest problem with SD Pancham is the low Speed and lack of priority; even if Pancham sets up an SD, it often struggles to make significant use of it. However, that doesn't take away from it being a solid wallbreaker. It's coverage is very good and powerful, and it's not easy to switch into, especially when you're expecting a Parting Shot. Speaking of which, in general, SD Pancham is worse than Parting Shot, because of the incredible momentum grabbing ability of the latter, as well as the potential to give an opportunity to set up. I think SD Pancham is in a similar situation to Scarf Scraggy, where it is worse than the main set, but takes advantage of the existence of that main set to force the opponent to play differently, giving it the ability to do things. As such, I think both Scarf Scraggy and SD Pancham should be one subtier below their main sets.
Life Orb Bunnelby C+ -> B-
Disagree
Man this hurts. I genuinely love LO Bunnelby and always enjoy using it, and it's one of the most powerful wallbreakers in the tier, having a similar amound of switch-ins to LO Doduo (hint: less than 5). However, it is not better than Scarf Bunnelby. LO Bunnelby struggles with its low Speed, though this is partially made up for with its access to priority in Quick Attack. I am going to also lump this on the pile with Scarf Scraggy and SD Pancham, as many opponents will expect Scarf Bunny, forcing them to play differently than if they knew it was LO from the start. Though I think the difference between LO Bunny and Scarf Bunny is smaller than the difference in the last two, it also has a harder time taking advantage of the surprise factor, since LO is revealed as soon as it attacks the first time, so it can only keep it up until it needs to kill something.
Life Orb Riolu C+ -> C
Agree
The Prankster nerf killed all Riolu sets, but this one in particular. It can no longer just assume it's never taking damage because it attacks first anyway and just kills something with +2 LO HJK, since Dark-types prevent it from doing anything at all now, and with Vullaby and Scraggy being as common as they are, Riolu really struggles to click Copycat. This hurts the LO set more than the Eviolite set, since the LO set doesn't have the bulk to take a hit and then fire off a 'manual' HJK, while the Eviolite set sometimes does. As such, this set should really drop, as it is pretty much completely outclassed by Evio.
Sturdy Aron unranked
Disagree
Essentially what this suggestion is, is wondering what Aron's niche is. Back in ORAS, I used Aron quite a bit, and eventually took a major liking to its Rock Head Rock Polish set, mainly for its ability to set up on one of the most influential Pokemon in the metagame: Fletchling. However, everything changed when Gen 7 attacked. Fletchling was nerfed into the ground and Fighting-types are everywhere now (granted they used to be as well, but even more so now that Fletch is dead). As such, Aron can't really set up on anything now, and even if it does, it just gets revenge killed by Timburr or Croagunk. So we can conclude that Aron's Rock Head RP set is bad now and I'd like to nominate it to
C-, D, or even unranked. In the meantime, since Aron is still C on the actual Viability Rankings for some reason, we need to keep a set there as well, and Sturdy is definitely the better set imo.
Eviolite/Berry Juice Salandit unranked
Disagree
I'm going to preface this by saying that I've never used Salandit, and that every Salandit I've faced just got trapped and killed by Diglett, so this is purely theorymonning. Salandit has a very interesting typing, which gives it both good offensive coverage and some nice resistances. However, its lackluster bulk means it can't take advantage of this typing very well to set up a Nasty Plot, as even resisted hits will often 2HKO. That is, if it's a holding a Life Orb. With an Eviolite or Berry Juice, it can make pretty good use of this typing and after a Nasty Plot, it's plenty powerful anyway, so it no longer needs the Life Orb. As such, I don't think it's really worse than the LO set at all, so I'll nominate it
to C.
Utility Mantyke C- -> D/unranked
Agree to unrank
Utility Mantyke is very lackluster. It is extremely passive due to the lack of investment, and can easily be taken out due to its lack of recovery and bad physical Defense. It just doesn't do all that much in most games to warrant being ranked. It was a mistake in initial tiering to even place it on here at all. However, Mantkye is still C- on the Viability Rankings, so we need to have a set on there as well. As such, I'd like to nominate
Rain Dance Mantyke to C-. The offensive Rain Dance set functions as a late game cleaner that utilizes its ridiculously good offensive typing (seriously. two mons resist Water/Flying, and one of them is Helioptile) to become very hard to switch into. It's still not exactly good, as its Special Attack is still lackluster and Hydro Pump is unreliable while Air Slash is weak, but it performs its role much better than any other Mantyke set.
Swords Dance Karrablast unranked
Agree
This is just bad. Karrablast is way too slow to make use of an SD boost, Bug is a terrible typing, and it's coverage isn't exactly good either. Scarf Karrablast at least has a niche as a revenge killer and cleaner. SD Karrablast just does nothing.
For the people who are going to respond to this, you don't have to do all of them like I did. Feel free to cherry pick my opinions if you really want to disagree with me, and go right ahead and pick the mons you want to talk about.