Time for my thoughts on some nominations and some of my own. I'll start with my thoughts on the others.
B- -> Higher (B imo): Agreed. Mamoswine has always been a huge threat to switch in to, and it seems to be criminally underestimated right now. Ground/Ice is an amazing offensive typing, and Mamo has the speed to pick off some threats such as Tapu Bulu, Heatran, Lando-T, Zygarde, Amoonguss, etc. While it does have some weaknesses such as its Speed not being able to compete with Tapu Lele, a poor defensive typing, and meh bulk, it is definitely not B- material and it seems to be much more consistent than the other stuff in B-. Mamoswine has become an anti meta pick due to its offensive typing being very favorable with the omnipresence of Lando-T, the rise of Salamence, and the fact that nothing can switch into it except for maybe Tapu Fini, Ferrothorn, and phys def Celesteela, but after some chip EQ is a clean 2hko on Max HP/Def Fini, and Fini is easy to wear down. Of the Pokemon in S, A+, and A, Mamo has a good matchup vs Lando-T, Heatran, Magearna, Tapu Koko, Garchomp, Hoopa Unbound, Magnezone, Tapu Bulu, and Zygarde. All the rest bar Celesteela and Ferrothorn can't switch in on it. When something with this much damage potential is ranked alongside Latias and Breloom, it just seems a bit off.
B+ -> A-: Neutral. I have no opinion on Scolipede. I can see arguments both for and against its rise. I would be fine with either.
A- -> B+: Agreed. The shift to SM hasn't been kind to Weavile. With the introduction of Fairies everywhere, Weavile got a lot of new checks and even counters. Tapu Fini can deal with it pretty easily, the common Scarf Tapu Lele neglects Weavile's priority and outspeeds and kills, and now we have a true counter in Magearna. On top of that, Weavile offfers absolutely nothing to the team defensively, and is even Stealth Rock weak. When compared to everything in A-, they all at least have the ability to switch into something. Weavile doesn't have this ability, except a Choiced Psychic move. Speaking of abilities, all of Weavile's are useless, which is another deterrent to Weavile. All in all, Weavile doesn't have the
ability to put an insane amount of
Pressure on teams like it did in ORAS, and offers absolutely nothing from a defensive standpoint.
C- -> C/C+: Agreed. Primarina is extremely hard to switch into, and has an excellent typing on top of decent bulk and a good movepool. It's not as niche as the stuff in C- like Decidueye (rip that mon, had so much potential), and I would say is arguably better than some of the stuff in C and C+ like Gastrodon, Shuckle, Minior, and Mega Garchomp.
Edit: Would also support a ranking of Rotom-Heat.
Now on to a couple minor personal nominations of mine.
C -> C-: I already touched upon this in an earlier post, but it was never mentioned again due to more pressing issues. Just gonna bring it up again since absolutely nothing changed for it to get any better.
C -> C+: I have been using this mon a lot and I've had success with it. With its great Electric/Flying typing and its Volt Absorb ability, its 79/70/80 go a bit further than it would on another mon. Of course, its Rock weakness is detrimental and it faces a lot of competition from Tapu Koko. However, I do feel like this mon is being slept on. Its 101 base Speed allows its Scarf set (its best set imo, but can also run Nasty Plot/Agility) to always outspeed +1 Salamence and OHKO it with HP Ice. Its Scarf set also outspeeds Scarf Lele and can revenge kill after some chip. This thing can revenge kill a lot of different common mons in the meta such as Lando-T, Garchomp, Tapu Fini, Tapu Koko, Greninja, Celesteela, and Zard Y. It seems under-ranked in C, with trash mons like Mega Garchomp , Magneton, Shuckle, and Xurkitree. Of course, Thundurus-T has its flaws, but C rank seems too low for it.