I love VoltTurn soooo much. Very good concepts you have going on here. But at the same time, you have way too many choice pokes. The most I'd suggest is 2. So definitely change some items around so your opponent can't predict around your team easily.
Rotom-W:Choice Specs>Chesto Berry
Very good if you need to keep the VoltTurn momentum up. It can bluff the choice item after they don't see lefties and switch in a ground type to force you to switch. Then all you have to do is KO them with hydro pump. I also would advise you to change HP fire to ice so you can hit grass types on the switch as well as dragon and ground types (aka gliscor and lando).
252 SpA/252 HP/4 SpD
-Hidden Power (ice)
You might want to change scizor to a life orb swords dance one for late game sweeping but if no, that's fine. Just might be very threatening for opposing teams since after +2, your opponent is going to wet their pants. And you might want to replace super power with quick attack to nail resists and dual priority can help out a lot
252 Atk/8 SpD/248 HP
And lastly, you might want to add lefties onto celebi. Choice scarf doesn't benefit it against Gastro since its already really slow and being able to switch from a special attack to u-turn can be very helpful. It also makes a Great Wall against breloom so extra recovery and if you are using it as status fodder can be very handy. You might also ant to replace HP ice with for instead so you can kill any scizors that want to pursuit trap you or uturn. This strategy can also help against ferrothorn and forretress that think its safe to set up hazards. And back to the scarf thing, 2 good scarfers in lando and Infernape handles most other scatters (except keldeo) with another one might be overkill sometimes.
What happenled to all the teams I wanted to win!?!?!? Sigh, go Detroit?