Right... My comment was in response to OP's suggestion. As I said, there should be some class definition where a weapon will be more or less beneficial to one particular player; they shouldn't be indistinguishable and deciding your class based on your weapon... is silly... hmm...
It suddenly occurs to me that these jobs we're talking about recently would all make much more sense as not being related to your 'weapon class'. As Cairdeas just said, you learn all swordskills as a gladiator.
However, I must point out that you also learn provoke, cover, and rampart, all of which have nothing to do with swords themselves and instead are more job-related skills.
What if... instead of sword users learning that, they learn base sword skills as per usual. Circle Slash and Onion Cut, maybe the elemental strikes (I say maybe because these become far more useful when the enemies are finally more developed and have not only elemental weaknesses, but the effects of your skills will actually matter as well).
Then you tack on, say, Paladin, and he also learns cure, provoke, rampart, cover, phalanx, etc. Things that will help him do his job and are only available to that job. And these spells (or rather, this particular combination of spells/skills) are only available while you have Paladin tacked on - it can also be tacked on to certain other classes once requirements have been met, but you can't use sword skills unless you are using a sword (and have Gladiator class). And of course you have the option of removing Paladin and tacking on something else.
Ideally such a system would have seperate SP for your weapons and JP for your jobs.
Con/Thm would have to be worked differently. Maybe I should start a thread of my own..?
Then again, I coulda sworn I've seen someone come up with a system just like this around here somewhere...
EDIT: Not being able to equip weapons on one class or another is an unnecessary game mechanic that realistically makes no sense. However, given that a white mage would generally have no reasonable sharpshooting skills makes it sensible to incur a penalty or require a special skill (They practice magic, not shooting people, after all.) And a gun isn't really going to help a white mage do their job much anyway.
Doesn't mean you should take the option away. Remember, some people are playing because they want to have fun. If playing a shooty-priest is how they wanna do it then that's entirely up to them.