If I had to think of a downside to this set (which was damn near impossible), it would be this
It is a bit situational, requiring you to have a completely open opponent, but each time you deal damage to a player with a creature enchanted with Breath of Fury, you get an extra combat step at the cost of sacrificing the enchanted creature, reattaching the enchantment to another creature
Mega Gardevoir ex's partner in this deck is Mimikyu ex, who's able to always stay on the field for multiple turns thanks to its Disguise Ability
The green deck tactic of resting and attacking Characters gets a helping hand from extra Characters to quickly pick up the pace
Showcase your Charizard 4/102 with a premium extended art display case designed for graded Pokmon cards
"It does happen on occasion." No matter how much testing you perform, once it's done, it's done