Nominating Porygon for S
Before I begin, I am fully aware that people may initially be a bit hesitant for this because we're so used to Mienfoo and Pawniard sitting at the top, but please hear me out.
Porygon's combination of bulk, power, and versatility is unmatched. No other Pokemon is able to function consistently and effectively as both a top-tier wall and an extremely powerful offensive threat the way Porygon can, and I believe that its incredible prowess at what it does is on equal footing with the current S-rank Pokemon.
Defensive Porygon is unquestionably the most effective bulky blanket check in the metagame. The sheer number of Pokemon that it is able to soft check is absolutely ridiculous, and by ridiculous I mean it is able to switch into standard SR Eviolite Pawniard and win the majority of time. Adamant Eviolite Drilbur's Earthquake fails to 2HKO after Stealth Rock, so if you can't hit harder than that, then yup Porygon checks ya. 26/16/16 bulk is comparable to Spritzee's 27/16/14, but unlike Spritzee, Porygon can actually be pretty tough to switch into, between its decent 15 SpA and enormous offensive movepool, and can recover its health instantly as opposed to relying on Protect, which is an enormous boon for a wall. These traits allow even defensive variants of Porygon to be much, much easier to fit onto more offensively-inclined teams; on the other hand, the sheer number of Pokemon it can check in a single slot, and its ability to countertrap Diglett, make it just as tough as Spritzee to pass up for defensive teams. I might as well mention now that it's one half of arguably the best core in the metagame, PORYSPRITZ, but Spritzee is merely A+; I'm trying to argue that Porygon is above that.
Enter bulky attacker Porygon, which is probably my favourite set to use in LC right now because it's just soo damn strong. Even if Porygon doesn't grab the Download boost - which isn't difficult to get at all when there are 13 Pokemon, as well as 5 specific sets for other Pokemon, out of a total of 60 Pokemon in the S/A/B ranks, that Porygon will not usually get the +SpA boost against (give or take a few because counting is hard) - its Tri Attack is comparable to Adamant Pawniard's Iron Head, certainly not easy to shrug off. However, if it does, then there are a grand total of 0 viable switch-ins to a simple set of HP Fire or Fighting/Tri Attack/Psychic/Recover. LO/Band Mienfoo has Trubbish/Koffing/Skrelp, LO Abra has Stunky/Munchlax, Gastly has Stunky/Chespin, even LO SF Cranidos meets its match in Hippopotas. Unless you're willing to use Specially Defensive Berry Juice Scraggy, in which case I counter with the equally viable Hyper Beam Porygon, there is literally nothing worth running that can safely switch into a Porygon set that only has a single, mostly unimportant variation in its movepool (the only difference between the two when it comes to viable safe switch-ins is that HP Fire leaves it open to Hone Claws Aron, whereas HP Fighting loses to Swords Dance Honedge and defensive Pumpkaboo). Of course, you could always sack a Pokemon and then trap a troublesome wall-breaker, but that won't work on Porygon, because its Recover can outheal LO Diglett's Earthquake. It's also much harder to force out with the threat of a revenge-kill, or simply play around with smart switches, because even a more offensive set like this one has 25/14/14 bulk before Eviolite; in fact, Porygon straight up wins against standard Taunt Mienfoo and Timburr in a lead match-up, quite the checks there. Its bulk is comparable to traditionally defensive Pokemon like Foongus and Timburr, which, by the way, don't rank amongst the hardest hitters in the metagame, and is certainly enough for Porygon to still act as a check to prominent offensive threats threats such as Fletchling, various Shell Smashers, and Sash Abra. The only Pokemon with a comparable level of both bulk and power to bulky attacking Porygon are Munchlax and Wailmer, but I do not think I need to go over why Porygon is many times better than Munchlax in the average match, not sure about Wailmer though.
I would like to emphasize Porygon's versatility some more here, because there isn't really anything else in the metagame quite like it. The main sets have a lot of variation themselves; for example, Thunderbolt can be run on either set to check Water-types, and Shadow Ball covers all of Pumpkaboo-Super/Gastly/Gothita/soon to be freed Misdreavus in a single slot. However, it also has a fair number of other, completely different sets that are viable, albeit not to the same extent as the main sets. Fast Trace Porygon is quite nice to better check Bellsprout and to annoy bulky Mienfoo, and still has as much bulk as bulky attacker Porygon, which is, again, very bulky. Agility Porygon is a decent late-game cleaner that itself is extremely versatile, between its item and choice of moves. Porygon can hit 14 Speed, allowing it to take advantage of its big damage with a Download boost to run a threatening Choice Scarf set. I think I've lost to OP's LO webs-abusing Porygon. There are a ton of other, more gimmicky options available to it, such as Trick Room, Toxic + Conversion, and Gravity, but I won't go into these; my point is that Porygon can do way too many things, and can be tailored to fit into just about any reasonable role.
I do not think that Porygon is on the same level as the other A+ Pokemon. Fletchling has one viable, somewhat predictable set, and has awfully unimpressive stats for all its revenge-killing prowess. Abra is much less predictable than Fletchling, but can still be played around without too much hassle, in that LO Abra is removed by all three trappers, and Sashbra is easily walled. Magnemite's Berry Juice set isn't too troublesome to deal with, and its Choice Scarf set struggles to gain momentum until Ground-types and Chinchou are removed. Porygon is unpredictable, difficult to play around, and requires basically no support to function. The only Pokemon that are as absurdly easy to fit onto a team as Porygon are Mienfoo and possibly Archen, but Archen is noticeably less reliable than Mienfoo or Porygon. I honestly feel that Porygon makes more of an impact in the average match than Pawniard does, because Pawniard is so easy to wear down and loses to a stray Hidden Power Fighting, whereas Porygon can stick around to mow things down throughout the match. I'm not calling for a Porygon suspect, as it rarely manages to get more than six kills per match, but I do believe that its strengths warrant a ranking amongst the best of the best.
Nominating Foongus for A
OK, so from what I understand, Foongus was originally moved down to A- because it's apparently useless after Sleep Clause is activated, which is pretty great except that it's blatantly false. Even without Spore, Foongus is one of the best available checks to all sorts of Water- and Fairy-types, while also handling Fighting- and Ground-types to some extent. Foongus is one of the best defensive pivots in the game by virtue of its typing and ability alone, as it can check some of the metagame's most important threats, as well as less seen but hugely threatening and difficult to check threats such as Corphish, over and over and over, in a way that can't even be played around bar Gothita, because pulling that sweet double switch does more damage to Spritzee than it does to Foongus. It's also not that easy to switch into, because Sludge Bomb's 30% poison chance, which is going to happen eventually because Foongus sort of lasts forever, really hurts things like Vullaby and Ponyta, and allows Foongus to just outlast its checks and counters without much of a problem. Gothita can be annoying if you're relying on Foongus as your sole check to things (doesn't want to switch in though), but the opportunity cost that comes with using Gothita is much bigger than the one that comes with Foongus, which is evident by how other Gothita-weak Pokemon are ranked higher than Foongus. All of that alone is probably enough to propel Foongus to the upper echelons of A- if not higher, but this is all BEFORE mentioning Spore, which is, needless to say, a pretty good move. The amount of things Foongus can do just makes it so easy to fit onto defensive and offensive teams alike, certainly on par with the other defensive Pokemon in A. Honestly, I don't know what else to say because I'm not sure why Foongus was allowed to drop in the first place tbh
Also supporting Gastly for A+ because cute and strong