I still stick by my thoughts that the new jobs may have exclusive weapons for them and retain use of items that the class that was required to obtain them is. We are still not sure how Jobs will be obtained for certain but I'll just repost what I said earlier.
Yeah but as an extension I doubt they will be able to use anything other than the class that it branches from weapon. Unless they make specific gear for the new jobs as well. Who knows! Maybe they will use the class's equipment + new job specific junk.
Lets say Marauder becomes.
Dark-knight
Or
Warior
Both jobs can use the Great axes, but Dark knights can also use Scyths, and Wariors can use Great swords.
We don't have enough information to go on, so I doubt that "Jobs" will span the entire class system but who knows for sure?