I'm going to cover some obvious thing and do some other nominations :
A -> Unranked : Goodbye and good riddance.
A+ -> A- / B+ : I already thought that A+ was way too high even when Arena Trap was allowed due to the splashability and overall effectiveness of Zard-Y compared to the other A+ ranked Mons, especially when Shed Shell on Toxapex became more common. I don't think that a drop will surprise anyone as you won't have Dug to remove Zard-Y's checks / counters like Toxapex, Crucibelle-Mega and to a lesser extent Cyclohm, which are going to be even better. Furthermore, the realease of both Diancie-Mega and Latias-Mega, which are both big threat for Zard-Y (especially the second one which is a full stop in most cases) and competitor for the Mega Slot doesn't help neither.
Unranked -> A+ : Diancie-Mega is in my opinion the best Mega currently available in CAP, and obviously the Arena Trap ban helps a lot. There's no CAPmon being able to safely switch on her, the Fairy STAB is extremly useful in a Metagame where Tomohawk and Colossoil are everywhere, and she all the tools she needs to break through Pyroak, Cyclohm, Fidgit, Arghonaut and Mollux too. Overall there are very few safe switch in and Diancie-Mega can also provide a good support with Magic Bounce since she can disable Stealth Rock from non offensive Tomohawk.
Unranked -> B+ / A- : Latias-Mega is probably one of the best switch in to Specs Volkraken as it will probably never run a SE HP just to hit her, as well as a good check / counter to some threats like offensive Tomohawk, Keldeo, Zard-Y, Stratagem, Non-Dazzling Gleam Koko... Despite her Dark weakness, Non-AV Colossoil has to be careful when trying to Pursuit trap her since Ice Beam or Surf will hurt and the rare Reflect Type variant fears nothing from him aside from U-Turn. However, it's a little unfortunate that Stored Power CM Latias-Mega can struggle a bit against Hazehawk, but can still prove to be dangerous against any kind of team if he packs the most needed move (either a coverage move, Refresh or Reflect Type). Latias-Mega is a pretty good defoger as well since she can threaten Tomohawk and Landorus T with the right move, among other SR setters.
A- -> A+ : I don't think anyone would be surprised to see Heatran rising after the ban of Dug, both SubToxic and Offensive trapper work extremely well and Heatran's typing and ability are just as good as ever to check threats like non Focus Blast-Magearna, Zard-Y, Tapu Lele... Being able to run freely Leftovers and Groundium-Z or Grassium-Z makes Heatran very effective as a stallbreaker. The simple presence of Heatran means that Volkraken can't locking himself into Fire Blast without being careful.
B+ -> A- / A: I think Zapdos is the best Pokemon to bring against other birds as it doesn't fear much from Tomohawk, Pinsir-Mega (unless he packs something like Stone Edge, which is unlikely), Celesteela and Cawmodore. It's a solid answer to most variants of the two currents S Mon as well as an effective Defoger thanks to his match up against them and Ferrothorn.
A- -> A : Sticky Web teams are very tough to deal with in my opinion and I think having a setter as good as Necturna available is one of the main reason why : aside from Skarmory, Malaconda and Sableye-Mega, who are either rarely seen or mainly on stall teams, when you probably don't really need Sticky Web now that Dugtrio is gone, Necturna pratically beats every other hazard removers as long as she packs the right move and / or item (Psychium-Z against Tomohawk and to a lesser extent Fidgit, STAB Power Whip against Colossoil and Tapu Fini, Shadow Claw against Mew and Kitsunoh and Stone Edge for Zapdos and Mollux). But don't overlook her other sets, because Ghostium-Z Shell Smash Necturna is brutal against any team which doesn't use Hazehawk or Clefable, and Band Necturna can basically lure in and kill anything you want. She also have plenty of usable set like Z-Geomancy, Belly Drum, Seed, Double Statut... So I think she definitely deserves to be ranked alongside with other metagame defining threats like Colossoil, Syclant...
A- -> B : Tapu Fini is, in my opinion, mostly outclassed by Arghonaut as a defensive Pokemon since this one checks / counters everything (or almost) that Tapu Fini wants to stop like Syclant, Volkraken, Ash-Greninja and Zard-X. Even though he may have a better defensive typing in most regard, the lack of recovery really hurts him and he cannot put a real fight back against most Arghonaut fears aside from Tomohawk. I would only use him over Arghonaut if I really need an Hazard remover or if I absolutely don't want to have more Fairy, Fly and Psychic weaknesses, because Arghonaut covers more stuff like Volcarona thanks to Unaware and is more easy to use in the long term. Fini is far from being the best Stallbreaker as well.
A- -> A : Even since Aurumoth doesn't have Illusion anymore and thus is less played, Unaware clefable is still very nice to have because of the huge amount of set up sweepers in the metagame and Clefable's weaknesses aren't too troublesome against most of them. Magic Guard sets are very good as well since Spikes are used quite often and Clefable fear nothing from them and thus can constantly switch during the match.
B- -> B+ : I know I already asked for a rise, but Gastrodon is just so easy to put on a team thanks to the number of dangerous things it can check / counter like Magearna, Koko, Greninja, Ash-Ninja, Volkraken, Mollux and the newcomer Diancie-Mega, and B- doesn't reflect that. One of the main argument against his rise was his passivity, but the fear of Scald burn and Toxic can really make him hard to switch into in some case, and it can be a pain to pass without Grass coverage, which is very easy to cover defensively.
B -> Somewhere higher : No more Arena Trap means that Stall teams will be crying by seeing him on the opposite team, and Hoopa-U is probably the deadliest Wallbreaker and the most difficult Pokemon to switch into, the Choice Scarf set gives him a much better match-up against offense and with Web support its just brutal.
I agree with a rise for the following mons : Krilowatt, Kitsunoh (I already explained why the Wishtect set is so damn effective), Toxapex, Mew, Mollux, Ninetales-A, Magearna, Kartana and Kyurem-B. I also agree with a drop for Rotom-W. I don't have much else to add about these nominations. I also think that Swampert-Mega, Kingdra, Alomomola, Revenankh, Cofagrigus and Porygon2 should all rise as well and that some Mons like Chandelure and Ditto should be added, but I'm tired of writting now.