Problem with Blue Mage is class balance and FFXIV's game mechanics. They're not going to learn ANYTHING from mobs (except maybe pretending to, in cutscenes) and they can only have mostly generic types of spells because real Blue Magic is is overpowered and gimmicky.

And more to do with this topic. I think Musketeer>Blue Mage has always been one of the louder assumptions about what Musketeer might turn into. I mean Corsair is definitely the most expected gun job but there's plenty of X-2 fanboys who've been calling for Gun Mages all this time. I can see Gun Mage as a possibility, but only if it's horribly homogenized into some lame generic support dps and I think support DPS is painfully assumed for the gun job.

I'm only going to feel that it's "not what people were expecting" if they make it a healer or tank or act ridiculous and choose something random and inappropriate like Musketeer>Time Mage