Flying gems are completely unobtainable in the newer games, so this moveset would be impossible. Even if you were playing a Generation 5 game with a flying gem, having both thief, acrobatics, and natural gift would be pointless because you might steal a leftovers that weakens acrobatics, prevents natural gift, and you can't get rid of. If you want to remove opponents' items in Generation 5 single battles, then use this set.
Gengar @ choice scarf
EVs: 4 Def / 252 SpA / 252 Spe
- shadow ball
- focus blast
This is better than Crobat because it can be a good revenge killer as well as cripple item-reliant Pokemon, while Crobat can only do one of those. Crobat also relies on thief, which is worse than trick because it can usually only be used once and can't force opponents to hold choice scarves.