Aegislash should definitely stay in S-rank, no questions asked. It poops on so much of the metagame and it checks the living hell out of top tier threats such as Thundurus, Deoxys-S, both Lati twins, Scizor, Terrakion, and much more. Not only that, but it also breaks down common defensive Pokemon with ease, making it easy for a teammate to come in a sweep once it weakens down their counters. It's also incredibly versatile, capable of running the classic mixed tank with King's Shield to screw with physical attackers, and all out attacker that's able to break through most walls with ease, and an SD or Autotomize to sweep. It's just got the perfect movepool for what it wants to accomplish, and it's absolutely terrifying to most offensive teams, making it a huge threat. Definitely stays in S.
Both Charizards are so good in this meta, and none of them should drop either. I don't understand why some people assume that they're only in S-rank because of the mind games they play until they mega evolve, because that's definitely not the only reason. Charizard X is one of the best sweepers in the meta bar none, and its ability to go bulky or offensive makes it that much more of a threat. Charizard Y is nearly impossible to switch into, and while it has a nasty SR weakness even after Mega evolving, Defog and Excadrill are so damn easy to slap on a team that it isn't much of a problem. Although it's hard to afford giving up reliable recovery to 2HKO Latias, the fact that you don't really know the last move it's running until it uses it is terrifying. Besides, if you don't have something like Latias on most of your teams, playing around Charizard Y is a bitch in general, because it 2HKOes a majority of the meta with just Fire Blast, forcing you to rely on checking it. Both are solid S rank, and arguably the best Megas in OU right now with Mega Luc gone.
Mega Pinsir is a tough one, but playing with and against it so many times, I think it deserves to stay S. Once its checks and counters are gone, nothing can stop it from sweeping. Even if its counters are still present, as long as they're weakened enough, a +2 Return is going to easily knock some of them out. Priority makes it very difficult to revenge kill properly without something like Talon or priority T-wave from Thundurus, and with EQ it no longer has to worry about being completely walled by Aegislash. Stealth Rock isn't too much of an issue because Pinsir isn't usually going to come in until late game to sweep, meaning that it's only going to be 25% weak to SR for most of the time. Besides, Defog is everywhere yadayada. It's just such an easy Pokemon to use and sweeping comes easy once its checks and counters are weakened.
Mega Venu is really controversial, and I don't think I have enough experience with it to judge where it should be. I've faced it countless of times, and while I've had times where it was really easy to get around I've also had instances where it never dies. I'll just leave other people to discuss it for now.
Most of the A+ rank also look fine to be honest. Kyurem-B is a god among Pokemon and is so good in this meta because of its Teravolt ability and insane attacking stats. Deoxys-S is still a really good hazard lead and its LO set sets it apart from Deo-D, who I think should move up to A+ because it's almost just as good as Deo-S in the hazard department. Rotom-W should stay in A+ because whatever defensive stat it doesn't invest in it ends up being pretty frail on that side, and it doesn't really have a reliable way of recovering its health without using ChestoResto, which gives up valuable Lefties recovery and after it's used once than you no longer have reliable ways of healing at all. This makes it pretty easy to wear down in general, which is why the infamous bird core is so deadly because of their ability to easily overwhelm Rotom-W and take advantage of its lack of reliable healing. It's a solid A+ rank though, simply because it's so anti metagame and it keeps a lot of key Pokemon in check.
Manaphy is an incredible sweeper, but it shouldn't go to S. It's pretty damn weak before it sets up, and what really sucks is that it's either walled by bulky Water-types or Mega Venusaur. It's also not that fastest Pokemon, making it relatively easy to revenge kill once it's weakened a bit. I could potentially see Thundurus in S simply because its priority T-wave is like the greatest thing ever and its amazing speed tier allows it to revenge a huge portion of the meta, and sweep relatively easy with Nasty Plot. It's a close one though.
Everything else looks fine.