I love the idea of bringing Dual type back. What I love even more is that even though Volcanion is Fire/Water, his attack only uses one kind of energy. That means he is more versatile. I've always hated the way Weakness and Resistance played out in the card games, because if you were playing a Grass deck against a Fire deck, it was an uphill battle all the way, but making a deck with several different Types is just not feasible when it comes to Energy. However, if they made Dual Type Pokemon, but made them predominately only use on kind of Energy, then it is easier to build a balanced deck. Like, oh, I'm building a Dragon deck. I'll include this Dragon/Dark Hydregion so I stand a chance against Fairy. And, oh, Fire is good right now in the Meta, so I will also use a Kingdra so I have that ability to use the Water-advantage. It opens up a lot of strategy.