Ghost types (excluding giratina) are really lacking in the BST department so this could be a nice addition.
I admit, a Ghost/Fairy would be AWESOME and it's one I've been rooting for the pseudo.
However I wonder if we even can get Ghosts with good BSTs now that Ghost is the new Dragon.
I mean, think about it. Only one type resists it, and only two types hit it for SE damage, one of those being itself. That's exactly how Dragon was before X and Y. However Dragon doesn't have two immunities or the passive ability to never be trapped by the opponent.
The only difference is Ghost types don't have great 120+ base power attacks and a bunch of 600 BST Pokemon representing them. Well, that and Dark both resists Ghost and is strong against it, which isn't the same as Steel versus Dragon.
But still, while this is great for Ghosts, it also may mean we're not going to see new more powerful Ghost attacks being released, and possibly no non-Uber Ghost that has a BST of 600 or so. I do hope that at least we get a widely-learned physical Ghost attack of at least 80 base power. Shadow Claw/Punch is just ugh. At least Shadow Ball's 80 base power is usable.
Because if Ghost got great new attacks they would probably become the new Dragon type that needs nerfing. >_>
EDIT: Agh, I keep forgetting Normal is immune to Ghost, so there is that. However Normal types hardly ever make it into higher tiers, even if they have a secondary type. --- I'm not against religion. I'm against all bad ideas, held for bad reasons, prompting bad behavior.