I'll sweep in from the side with some techs. While M-Rayquaza-EX is powerful, he has a few limitations. One of them is Safeguard. Having all that power doesn't help if your target is immune to Pokemon-EX! A small Raichu line seems like a good choice, as it only needs a DCE to attack, and operates off the number of benched Pokemon, much like Rayquaza. Even if Sky Field is countered, a bench of five Pokemon will do 100 damage with Circle Circuit - enough to Knock Uut a Suicune PLB or Sigilyph DRX / LTR. It can also one-shot an opposing Rayquaza in the mirror match in the off chance they can't get an Altaria out, and is a nice choice of attacker if you can Lysandre and one-shot a Shaymin to win the prize trade.
After testing, Jirachi-EX is also a nice tech. It seems to have been left by the wayside by some players in favor of Shaymin, but Jirachi's instant search for a Supporter is great for consistency. It's almost like having five Shaymin-EX in your deck!
So, with that in mind, my additions are...
+1 Pikachu XY
+1 Raichu XY
+1 Jirachi-EX