I sort of wish players could only choose one job.

[KyahAlmasy]

You're being silly. Limit breaks being the sole determination of someone's "job" which is generally their role in the party lest we forget... it doesn't hold up under scrutiny.
Just imagine if I have my Irvine set to do nothing but heal... simply because he has shot limit breaks you'd call him a Ranger rather than a White Mage though his role is that of a White Mage (and malleable at that)?

Quite silly.

That would be like me, as a white mage wanting to be a DD because I have elemental spells. Making me a black mage, despite the fact that my arsenal of abilities suggests otherwise.

The spells you decide to use with them, doesn't change that the abilities unique to them classifies them in a job. Heck, even the wikis reference the characters with these jobs. You're simply trying to split hairs.