Obviously, this is a drastic retyping. The last Fire/Ghost Pokemon that I can think of off the top of my head is Chandelure from Black and White. that turned out to be an extremely powerful Pokémon and actually proved itself in competitive play. while Marowak had always been a cool Pokémon in their design, he wasn't really one to build your team around. Now they have great typing and potentially another unique move or two as he did with Bonemerang and Bone Club in their normal form. I'm really excited to see how trainers utilize this Alolan Form Marowak in Pokemon Sun and Moon, and I'm definitely looking forward to training one.