BTW anyone considered running MegaMewTwo X as Calm Mind user ? He still has great 154 base SpA, good base speed and great second STAB to use, while allow you to beat stuff like Specially Defensive Tyranitar 100% of time thanks to 120 base power Aura Sphere (or if you feel brave, Focus Miss is still there) and Fighting typing makes you take much, much less damage from moves like Scizor or Genesect U-Turn, TTar Crunch or Darkrai Dark Pulse. Also thanks to STAB Fighting you could open up your moveslot for something else than fire attack to cover Steels. Sounds interesting on paper, although I would need to check calculations.
Or Physically Defensive StallTwo MewTwo X with Reflect/Recover/WoW/Taunt sounds decent as well, especially when Fighting provide you resistance to Rock (and you still have for example resistance to Fighting) and you only take neutral from Bug and Dark attacks, making you even better against those types. While at first it may get some heavy competition from Fighting Arceus - it's faster, with Reflect + Wow it's bulkier on physical side and Taunt allows you to beat stall teams as well. Just some food for thought.