I'd love to see this implemented; I keep getting really low-level dungeons on my dragoon, and while I don't mind, I'd MUCH rather do them as a lancer, since sometimes being able to toss out a heal or a couple of marauder skills (Which I can't use for some reason as a sub-30 dragoon, even though my marauder is only 15?) would make a huge difference.

Though really, they should just allow you to equip or un-equip your job crystal in an instance.