Yes, I understand what are you trying to do... If Regirock, Regice, Registeel, Kyogre, Groudon & Rayquaza have their own battle theme... Why does Mewtwo have a bare wild Pokémon battle theme??? That's not fair... But also it must be a little kind of difficult to get a great theme for Mewtwo, unless you are a Nintendo's Composer.
And well, you almost got it... Maybe some more symphonic cuts and more epic arrangements could give it the right tune... But dude, this work is amazing.