This is terribly naive, if I may voice my opinion. Do the calcs say that CAP 6 can be defensively walled? Of course. Here's the rub, can the defenders do anything back?These pokemon can all still threaten CAP in rain if it's carrying Aqua Jet. Skarmory in particular is still a full stop, and Rotom-W takes Aqua Jet just as easily as Bullet Punch. Ferrothorn too. Jirachi still checks Intimidate CAP with Electric moves or Body Slam. Scarf Keldeo still checks it too. Latios and Breloom would much prefer CAP to run Aqua Jet over Bullet Punch.
Skarmory has Whirlwind I guess, but offensively it relies on Brave Bird (chipping it's own health) or tries to set up Spikes or Stealth Rock, giving CAP counter time to belly drum up and clean house, and that's not getting into Skarmory under Intimidate. (though I suppose CAP could be taunted)
Ferrothorn is similar. What offensively can it do to threaten CAP out? nothing, it carries Gyro Ball and Power Whip, both of which are ineffective And while it stacks Spikes, CAP sets up to clobber it. About it's only option is to Thunder Wave.
Rotom has it's Water Stab resisted, and it's Thunder(bolt) potentially useless against an immunity.
Defensively these are great, I agree, but you can't call them legitimate checks unless they actually threaten the pokemon they're defending against.
So for Aqua Jet at least, I'm going to throw my support against.
Edit: OK, conceded, I hadn't thought of those options, but the point still stands that it's not a complete slam dunk in the defender's favor either, especially on certain sets.
Here's the tricky thing with Acrobatics, and other moves in particular. We are dealing with essentially 2 attacks stats here. Pre-setup, and post-setup. we have a big potential to make a decent move ludicrously powerful if successful setup is achieved, and a poor move into usable. That's tricky.
Here's the question we have to ask ourselves mostly here, and I mean this in all seriousness. Would being able to obliterate all counters truly be a bad thing... post set-up?
That's the true question. With Belly Drum in play, we could potentially use that higher attack stat and make an easy sweep the reward for the tricky achievement of setting up.
We already have calculated potential revengers that can outspeed and chip down CAP.
Now I see problems with this idea, Leftovers being a big one, but Substitute can also move the bar one way or another. It just depends if we want to go in that direction. Most posters seem to be leaning twards no.