Here are a couple changes I'd like to see happen in the B ranks.
Sylveon for B
ARE WE JUST GONG TO IGNORE MY BABY?! D:<
I've stated this in this thread once and in the new Sylveon thread, but with most of these new Mega Evolutions being physical attackers, such as Mega Gallade, Mega Metagross, Mega Swampert, Mega Beedrill and Mega Lopunny, having a special-attacking Fairy-type wallbreaker to get past physical walls such as Mega Sableye and Mega Slowbro that does not take up a mega slot (uh-hum, Mega Gardevoir...) and even has the ability to be a pseudo-cleric with Heal Bell and gain momentum on her opponents with Baton Pass, Specs Sylveon got WAY better in ORAS. It also helps her case that Megas like Mega Sceptile, Mega Altaria, Mega Lopunny, Mega Gallade and Mega Latias are known users of Substitute, meaning they are not safe from a Choice Specs Pixilate-boosted Hyper Voice. Base Metagross is nearly OHKO'd by a Shadow Ball, as well. Good luck switching in! The factors keeping her away from B+, however, are her painfully slow speed of 60, her really low physical bulk of 65 and the reliance of a choice item to perform as a wallbreaker, but I strongly believe that despite all that, she's a lot better than the pokes residing in B- atm. Definitely better in ORAS OU than Mega Houndoom, Doublade and Mega Garchomp.
Raise Sylveon to B rank.
Base Scizor for B+
In XY OU, it was foolhardy to use normal Scizor over its Mega, but while Mega Scizor is still very good in ORAS OU, its base form has gotten much more common with the introduction of new megas, as it is no longer as big of an opportunity cost as it was in XY OU. With threats like Mega Diancie, Mega Altaria and Mega Beedrill being very weak to Choice Band Scizor's Bullet Punch, this allows you the option to run another Mega Evolution of your choice while having the benefits of Scizor on your team. Scizor can also still perform the role of a bulky defogger, a role you wouldn't want to run on a Mega Scizor. Seeing what's in B rank as well, I believe base Scizor is better than Omastar, Quagsire (he has REALLY fallen from grace, sadly :c ) Lucario and Mega T-Tar.
Raise Scizor to B+.
Empoleon to B.
Being one of the very few checks to Greninjas not carrying Low Kick and being the only Pokemon I can think of that 4x resists Ice, Empoleon definitely deserves a promotion. Water/Steel is a wonderfully unique and fantastic typing that gives it plenty of resistances (again, ICE IS 4X not very effective!!) and immunity to Toxic. If Greninja isn't running Low Kick (note that Empoleon is also immune to Gunk Shot), he's not breaking past this emperor penguin. For a defensive Pokemon, having a special attack stat of 111 is amazing, giving this special wall a bite to complement its long list of utilities, which include being a stealth rock setter, defogger, phaser and even a Choice Specs user if you're brave enough. Empoleon isn't without flaws, which imo keeps it from anything higher than B. While having a stellar typing, said typing is still weak to common attacking types, such as Fighting, Ground and Electric. Having no reliable recovery also hurts it, and its speed isn't stellar at 60.
Raise Empoleon to B.