hi i'm better at this tier than I am at XY so i'll actually comment after playing in SPL
Wobbuffet from B to B+
This thing is absolutely ridiculous on offense, especially with Mega Mence. If Wobb gets in on support Arceus, CM Arceus, etc. they have the choice of attacking and dying or spamming Recover / Defog / Calm Mind and turning themselves into set-up bait. Early game, Mence can use the free set-up to blow holes into Tina-O / Groudon / etc, and mid to late game it can use them to sweep. Since heavy offense often doesn't use a scarfer, strong opposing scarfers can be very problematic. Wobb fixes any worried about being cleaned up by Scarf Xerneas, Genesect (lol), or what have you. It's also an excellent Mewtwo check, a Pokemon that was underused in SPL due to opportunity cost but is still an extremely good and versatile Pokemon that can terrorize most offensive teams. I know Dice likes Custap, but Leftovers is perfectly viable if you want an extra set-up opportunity in exchange for a potential clutch late-game Destiny Bond or Encore. I used Wobb + Mence twice in SPL vs. mm2 and Problems, and they did severe damage vs both teams before Wobb was frozen by Ice Beam. Excellent Pokemon, I cannot believe some are seriously pushing for C+ or below.
Mega Aerodactyl from C+ to B-
This has a very clear niche on HO hazard stacking teams from checking Ho-Oh once, revenging mm2y and many Scarf users, and by far most importantly getting both SR and Defog on the same set. It's not a great Mence check by any means but at least it cannot set up on you! It isn't outclassed at all in its role, which is why I argue for B- instead of C+, although Aero isn't gonna fit onto anything that isn't HO so I won't argue for B. It also revenged weakened EKiller since they are usually Jolly and take good damage from Stone Edge, so there's that. Aero bops Diancie with Earthquake, but gets smashed by Sableye unfortunately.
Forretress from C to B-
Already talked about this, but it's a good lead despite being terrified of Darkrai. Most Taunt users despise Gyro Ball (Mewtwo / Deo-S / Aero) and like Aero, it can beat 1 out of the 2 viable Magic Bounce users. Custap Berry FTW.
Alomomola from Unranked to C-
I brought offense during SPL because I didn't want my games to drag on for very long, but anyone who playtested with me knows I like Stall quite a bit in ORAS. Alomomola is an excellent Ho-Oh switchin (since phys def Toxic is not relevant at all in this meta) that can pass giant Wishes to its teammates. It also gets Knock Off to aggravate STAG users, particularly Gengar switches. You should still use this with a Flying resist bc Brave Bird pressures it immensely, and this struggles to wall Salamence since they often carry Refresh. This also annoys Life Orb Extremekiller, Primal Groudon, Kangaskhan, and to a much lesser extent SD Groundceus. It's sorta decent in a physically oriented metagame, but struggles to fit Scald onto its moveset bc it needs Toxic, and is obviously set-up bait for a fair number of Pokemon. It's viable though. Dice if you read this, FUCK YOU lol this is getting ranked.
Mega Kangaskhan from B+ to C+
OK sorry Dice, that was uncalled for. I'll apologize by arguing for Kanga's demotion. What niche does Kanga fulfill in this metagame??? Aero has SR + Defog, Mega Gengar has Shadow Tag, Sableye and Diancie have Magic Bounce, Mewtwo X and Y are both still deadly as hell and provide great speed, coverage, and potential set-up opportunities for Xern etc. with Taunt, Scizor gives Stall teams a Pursuit user and Xern revenge killer, and Mega Salamence is rather good. Even Blaziken is pretty cool with HP Ice, it can lure and kill things just like Kanga can and gets Speed Boost to pull off cleans, something Kanga will never do. Sorry, but spamming Fake Out and hitting fairly hard with normal STAB isn't enough for this to be B+, especially with its embarrassing lack of synergy. It's countered by a great Pokemon (Ghost Arceus), has severe 4MSS, and is vulnerable to Rocky Helmet shenanigans. Most important, Kangaskhan does not hit hard enough to overloads Extremekiller's checks, which is the main reason why you'd use it. Lugia, phys def Yveltal, Ghost Arceus, defensive Salamence, etc will stonewall this mon unless you get exceptionally lucky with crits or Crunch defense drops. IDK why you'd ever use this on balance with the terrible defensive typing it offers, but SPL All Star Steelphoenix can defend this if he wants. Fake Out is nice when you face the sample team I guess, but Sableye is a better anti-sample team mon anyway. This Pokemon is mediocre.
I'd also move the following, though fell less passionately about them:
Greninja down from C+ to C (dice and I determined that forry is usually better)
Palkia down from B+ to B (VERY dangerous Pokemon, but I tried my ass off trying to make a team where it fit and never did...hardly checks any top threats)
Heatran down from C to Unranked (seriously i'd use Omastar before this, what the hell is it reliably checking besides fucking CM Fairyceus? Hack and Dice also hate this.)
Aegislash down from B to B- (slightly overrated as a Pursuit trapper, Problems doesn't like it either, Gengar can still beat you or severely hurt you with Hypnosis / Shadow Ball / the rare Will-O-Wisp and I'd rather use Scizor than Aegislash 95% of the time despite the opportunity cost of using a Mega. Also Primal Groudon exists now)