Ok, so I've been doing a lot of theorymonning for this meta and I've come up with a few sets.
Offensive
Shuckle @ Lum Berry/White Herb/Something else
Ability: Sturdy
EVs: 252 Spd / 252 Atk / 4 SDef
Adamant Nature
- Shell Smash
- Earthquake
- Stone Edge/Rock Slide
- Knock Off
Shuckle is a dangerous set-up sweeper, with Sturdy to guarantee it gets a smash off, and amazing EdgeQuake coverage. I honestly have no idea what item to run on this, but Lum Berry and White Herb seem good. I'm not sure if it's actually any any better than Cloyster and other Smashers, but it certainly seems good.
Swoobat @ Leftovers/Life Orb/Lum Berry
Ability: Simple
EVs: 252 Spd / 252 SAtk / 4 SDef
Timid Nature
- Calm Mind
- Stored Power
- Air Slash
- Energy Ball/Something else
Simple Calm Mind Swoobat is dangerous in NU, and even more so in a tier where it actually has good stats. Psychic is an option over Stored Power for more power off the bat, but Stored Power is much cooler. Basically, come in on a weak special attacker (something choiced into a move you resist is ideal), set up a CM or two, then go to town. This is a set that really wants Sticky Web support to avoid losing to speed ties and scarfers. And speaking of Sticky Web, the best setter in the tier is probably this:
Surskit (M) @ Life Orb
Ability: Swift Swim
EVs: 252 SAtk / 4 HP / 252 Spd
Timid Nature
- Sticky Web
- Hydro Pump
- Signal Beam
- Ice Beam
Of everything that gets SW, Surskit has by far the best typing. It also has a surprising wide attacking movepool. However, as Treecko pointed out, Sticky Web is somewhat weaker in a tier where everything is bulky, so this is probably best used on a Hyper offense team full of set-up sweepers.
Exploud @ Choice Scarf
Ability: Scrappy
EVs: 252 Spd / 252 SAtk / 4 HP
Timid Nature
- Boomburst
- Ice Beam
- Overheat
- Shadow Ball/Surf/Focus Blast/Whatever you want
Scarfers are very good in this meta, outspeeding everything that isn't also scarfed or boosted. Exploud's STAB Boomsburst is one of the most powerful attacks in the tier and can hit Ghosts thanks to Scrappy. Exploud also has an amazing movepool, containing such moves as Surf, Ice Beam, Overheat, Shadow Ball, and you could even go mixed with Hammer Arm, EQ, and Rock Slide. This makes Exploud an amazing, and very unpredictable revenge killer.
Linoone (M) @ Salac Berry
Ability: Gluttony
EVs: 252 Spd / 252 Atk / 4 HP
Jolly Nature
- Belly Drum
- Extreme Speed
- Return
- Thief/Shadow Claw
Linoone has access to Belly Drum + STAB Extremespeed, however is generally considered pretty mediocre even in NU due to its lame stats. However, with better stats it will be absolutely monstrous, especially with Salac Berry boosting it's speed after a Belly Drum thanks to Gluttony. Make sure to run 4 HP Evs in order to hit an even HP number so that your Belly Drum takes you into Salac range. Linoone's power after a Drum is ridiculous, cleanly OHKOing offensive Pokemon with Extremespeed.
+6 252 Atk (custom) Extreme Speed vs. 4 HP / 0 Def Mew: 435-513 (127.1 - 150%) -- guaranteed OHKO
Unfortunately, Linoone has no real option to hit Steel-types with, so you may want to run a Magnet Pull pokemon to remove steels before going for a sweep. Theif or Shadow Claw can be used to hit ghosts. Thief seems really cool alongside Salac Berry, letting you get an item to replace your berry. On top of this, Linoone can be a good revenge killer before BD with E-speed. Seems like a metagame defining threat to me.
Defensive
Let me introduce you to what I think is possibly the best defensive core in the tier:
Amoonguss @ Black Sludge
Ability: Regenerator
EVs: 252 HP / 252 Def / 4 Spd
Bold Nature
- Spore
- Clear Smog
- Giga Drain
- Stun Spore
Corsola @ Leftovers
Ability: Regenerator
EVs: 252 HP / 252 SDef / 4 Spd
Calm Nature
- Recover
- Stealth Rock
- Toxic
- Scald
These two cover each other's weaknesses almost to perfection, both have regenerator (anyone who has played with or against Amoonguss + Slowbro cores should know how good this is), and both get awesome support movepools. You might want to play around with the sets a bit (I made these in like 2 minutes), but I think this core should be very challenging to break, able to handle almost any threat.
Furfrou @ Leftovers
Ability: Fur Coat
EVs: 252 HP / 252 SDef
Careful Nature
- Roar
- Toxic
- Return
- Thunder Wave
Furfrou is basically unbreakable on the physical side even without defense investment, and is very bulky on the special side too. It also has quite a few other options: Protect, Sucker Punch, Refresh, and U-turn all seem usable as well. A Work Up set seems interseting as well.
Quagsire @ Leftovers
Ability: Unaware
EVs: 252 Def / 252 HP / 4 Atk
Lax Nature
- Recover
- Scald
- Earthquake
- Toxic/Yawn
Puts a hard stop to any boosting sweepers thanks to unaware. Probably will get used just because it can beat Linoone 1-on-1. Also stops Swoobat and Shell Smashers. Quag will be a very valuable tool for stall in this meta.
Other Notes
- Trick Room is interesting in this meta, as there will be no super slow things that can come in and take advantage of your Trick Room. Just minimizing your IV's should be enough to outspeed everything under Trick Room. However, it suffers from the same issue as Sticky Web; your Pokemon just dont hit hard enough for it to be worth it most of the time, especially seeing as TR is limited to 5 turns, thus setting up boosts isn't really an option.
- If you have 4 random EV's left over, and you aren't yet invested in speed, put them in speed just to outspeed uninvested things.
- Speed lowering Hidden Powers are really lame.
- This meta seems more luck based than others, seeing as speed ties will be more common.
- Weather seems quite strong now that Pokemon like Ninetales and Abomasnow don't suck, and a lot of unique abusers that are stuck in the lower tiers due to poor stats become absolutely terrifying with good stats - stuff like Cherrim, Castform, Walrein, Glalie, Jumpluff, Phione, etc.
- Megas are lame, effectively becoming normal Pokemon, just with no item.
Altogether seems like a very interesting, diverse, and fun meta, and one that I think I will be playing for quite a while. :)