Just thought I'd chip in here, because why not, it seems interesting. The two hot points here seem to be Stealth Rocks and Mega Sceptile, so here I go.
Mega Sceptile
I really like this thing as a Greninja counter, provided you aren't coming in on Ice Beam. It's ability to force it out, as well as other things provided it's amazing coverage, are really something. Not to mention it's fast as all hell. EQ kills Koko, who would otherwise leave a serious mark with HP Ice, and the only thing I can see walling this thing to any extent is Celesteela. It's fast, moderately bulky (v e r y moderately), and hits really hard. I can see it being a counter to a bunch of things, namely Greninja, Koko, Toxapex, and more. You need to be scarfed or named Mega Alakazam to outspeed this thing, and things like Landorus and Bulu have so few ways of denting this thing they have to flee on the spot. All in all, I think the amount of prominent stuff Sceptile checks is gonna make it a pretty big thing once it's allowed in PS.
Stealth Rocks
Paying careful attention to what Gary said, I have a few choice words on Rocks. One, it's a very over centralizing move, as 90~% of battles nowadays are won with some form of entry hazard support, Rocks chief among those. Whether or not the meta is better off without Rocks is not my call, and I'm not by any means whatsoever saying it would or wouldn't be. However, I do raise you another point, one that's been stated so far, and that's that most hazard setters are already great, and viable Pokemon, as well as vastly outnumbering and overpowering the few viable removers we have. Zapdos, Latios, and Skarmory are about the best viable hazard removers around, and while Zapdos has means of pressuring many setters, it also invalidates your own hazard setters. Spinners are a complete crush on momentum and really hard to bring in safely, as Excadrill isn't the fastest thing around, Starmie can't do much in the hit-taking category, and Tentacruel just plain sucks nowadays becuase Psychic STAB exists. Now, if you want to be that one weirdo who uses Tsareena as your spinner, you go right ahead. HOWEVER. In Rocks' defense, it keeps things like Dragonite, Mega Pinsir, and Charizard Y in check very well. It's easily the best form of entry hazard, and is certainly a strong point nowadays.
TL;DR: Mega Sceptile is pretty hecking good as a check to a bunch of stuff, and setters of Rocks outweigh the removers pretty bad.
You and I have very different definitions of counter if you think Mega Sceptile is a Greninja counter lol. Also why does it need EQ to kill Koko when EQ doesn't even OHKO and Leaf Storm OHKOs? You also forget to mention that Assault Vest Tangrowth walls MScept to hell and back (unless I'm missing some mystery coverage move MScept has). MScept does heavily deter Thunderbolt spamming from Koko but HP Ice Koko exists, meaning it's far from a counter.
Also did you talk about Defoggers without mentioning Mew? Mew's easily my go to Defogger atm - it handles annoying megas such as Mega Medicham, Mega Mawile, and stealth rockers such as Lando-T, Garchomp by using Will-o-Wisp and beats many of the more common Stealth Rockers - it walls defensive lando to hell and back, SD still doesn't appreciate a burn, nor does SD Garchomp (most are running Z moves or LO from my experience). While Ferro can annoy it, it still doesn't appreciate Wisp and it certainly doesn't appreciate the mons Mew is paired with that require the Defog support in the first place (Volcarona, Mega Zards, and MPinsir puts a chunk in Ferro). It also deters non Dark Pulse Greninja, outspeeds and wisps Adamant Bulu, while avoiding being trapped by TTar by Wisping, which cuts 80 BP Pursuit down to only doing 54% max. Unfortunately, Heatran walls it and keeps rocks up vs it, but it troubles the other Defoggers you mentioned as well. I agree hazard control options are a bit limited though in contrast to the number of stealth rock setters. Unfortunately, they don't affect Doubles much so I doubt anything will be done by Game Freak.