Why would they be problems? Who's to say RDM couldn't be an off-tank with magic?

This is why I hate the Armory system over XI's job system by the way - every traditional job in FF is going to have to have some stupid base class and then branch off into 2 or more different paths, but all with the same subset of basic skills;

This is why I detest ACN and SMN and how they both feel so completely wrong compared to not just their XI counter parts but throughout the series (well, just 3 in SCH's case but XI's was such a brilliant, masterful rendition of what was originally a deadbeat job that was only valid for literally 1 fight in the whole game). It also precludes BLU for 2 reasons:

Like RDM, it's traditionally a sword user but more more importantly, BLU is supposed to learn all its magic from enemies. Well, that doesn't really mesh at all with the armory system as it currently exists. And unless they introduce a subset of swords (sabers/rapiers) I don't see how RDM could be based on anything but GLD, which is fine for its melee side but awful for the magic side (not to mention I still feel ACN's spells like Bio and Miasma really belong more to RDM and DRK)