Yeah you can probably get it cause there's no way to get Cubone in ORAS. XY and ORAS Cubones should be the same : http://www.serebii.net/itemdex/thickclub.shtml
Well, Scrafty and Ninetales are really strong Pokemon. Personally I find these events very appreciative of Pokemon. Getting Beldum in Reborn is probably one of the most satisfying feelings ever.
Ability Capsule changes the Ability to the next one and not randomnly, I think. Say, if you have Intimidate, it will always go to Quick Feet and a second capsule will bring it to Moxie.
Boufallants and Tauros are amazing for Physical Sweepers. They're EVERYWHERE, there's 2 healing spots nearby and they give good exp. Also, the forest in North Adventurine has mostly Speed EV Pokemons
I'd say just catch about any Pokemon that's somewhat reliable. Sometimes you might have to switch your team around in case it gets too hard. Look after your money though as theres not many reliable sources of income.
I wish the berries would still reduce the EVs by 100 though. I understand that "casual" players probably wouldn't like they're stat to go down by 25 for just using a berry, but it's much easier to fix with the berries. Of course, with Hordes EV training is super easy.