The balanced the system, how exactly is it gimped for both DOW and DOM to have the same amount of skills/abilities. You are pretty much saying let's give mages 100 abilities and the melee can play with 5 since you want it the XI way. Also BLM isn't gimped it's the traditional BLM, their most defined elemental spells are ice, fire and thunder giving them all elements was something done in later games but only to simplify things. Even in FF Tactics BLM only has Fire, Ice and Thunder.

Also how do you expect them to introduce new classes if you give BLM all the elemental utility? So sure as it stands now THM is single target thunder, AOE Fire combos and a non combo ice line. What's the stop them from introducing a mage which specializes in ice combos and single target fire? That's the whole point of the armoury system you level other classes to add elemental spells you might want, why you might not have access to the combo or the whole line of spells you'll at least be able to make use of said elemetal in a different way if you want a single target fire or an AOE thunder spell.

It's perfect as is, giving a mage class to much elemental utility would just OP them in the sense that now they can handle any situation so why don't we just do mana burn parties rather than using melee which don't grant any bonus when hitting foes of with an elemental weakness.

Just be patient they'll add more mage classes later on and it will be easier for them because of how they've redid magic for THM/CON it allows them to be more creative and flexible with what they can create and once we get 2-4 more mage classes then we'll most likely have a decent variety of elemental spells ranging from single target, enfeebling and AOE.