seems to me the devs noticed that blue mage would need lots of maintenance to be a full job, i'd be all for it but feel the devs dont think the playerbase is "bright enough" to latch on so they released this gimpy locked away version
If blue mage was up to me it would be a complete job just a way more in-depth and personal one, it should be the jack of all trades choice, able to tank, heal or dps depending on its variant.
pretty much keep it so they need to go fight monsters of all types for abilities which would let them use whatever they want in the open world and be op as ever, then for duty content have it get detuned and have it setup so all of those myriad abilities have affinities towards dps/tank/healing so the player can form rotations based on them that would set their "variant" or what they would run that content as. I feel it should be a dps at its base with avg healer and tank stats when needed.
BUT unlike the other jobs that are locked in duty the blue mage should be able to switch if needed, lets say your tank goes down, the blu should be able to switch until the tank is back up or vice versa if a healer was incapacitated.
the issue with my idea is that it places work on players who want to play it and thats the plan, it would weed out those who dont wanna put in the work for it, it would be designed to protect other players, pretty much locking a blu mage out of group content until it's (1) found all of its abilities (2) built all 3 of its rotations, it would be a monster of a job to build and upkeep but I feel it would bring with it a big sense of accomplishment to those players that work with it.
overall I envision it as a solo monster, able to go out and lay waste to the world but when grouped together balance its open world freedom with the ability to be a clutch job that can cover for others when needed.