I love this deck (I was looking into it at one point myself) and am currently working on a Mega Alakazam deck that is using the similar strategy of using Pokémon like Hoopa, Spinda, and Meloetta to do the spread damage. One option that I've considered that might work really well for this deck is a combination of Spinda, Hoopa, and Meloetta. If you run 1 Meloetta, and 1-2 Spinda along with your 2-3 Hoopa, you will consistently have an attacker to spread damage. Ideally, you would be able to start with either Spinda and Meloetta to allow Mega Gallade to attack the bench, and then switch into Hoopa to place additional damage strategically across the board. I few other attackers I would look into are Trevenant Break (although it's slightly clunky, and lacks item lock, it does force your opponent to attach additional energy for their basic Pokémon to attack, and is a perfect Mewtwo counter because one of it's attacks deals 70 damage plus 10 for each energy on your opponent's Pokémon) and Meowstic (the idea of having Meowstic is that you could add lots of damage counters on the board with Mega Gallade and your other attackers, and then move the damage to either setup future KOs, or ideally KO multiple Pokémon like Shaymin). Also, if you are focused on continual draw vs bursts of speed, I would look into an Octillery N combo, because I have found it to be very reliable for yourself, and disruptive for your opponent (a buffed up Judge line would work just as well as N though). I honestly am not sure about how you will make space for any of these cards, but thought I would mention them in case any catch your attention. Hope this helps!Another good alternative to Hoopa and it also has similar qualities to promo Meloetta. However, this Spinda is Colorless; so, it does not present a real, alternative threat option to M Mewtwo EX (which is one of my concerns). But, as a starter, I think this is another solid option.