I Just wanted to point out an "impossibile" idea, but you know.. dreaming Is free..
What if BLU remain as It Is, but if you find all of its spells you unlock a new Quest that unlocks 3 new Jobs (with 3 differents crystals)
TLU (Tank blu) DLU (dps blu) and HLU (healer blu).
So.. you keep the limited job as It Is, with all its jimmicks, and you create 3 new REAL Jobs that use Blu skills as base (not all of them of course).
So for example pom cure Will become the standard gcd heal of Hlu, diamond back the invuln of Tlu, excetera.
The LITTLE problem Is that 3 new Jobs would Need to be designed almost from scratch.
Also something Need to be done about the lore and when new contents, spells and levels Will be added.. but you know.. i'll do It in my spare time if se allows me lol..