All the roles fighting over BLU

[Cabalabob]

I think BLU wont come with a class like DRK, AST and MCH. And in the mind of the devs it was a big failure to make two jobs evolve out of one class (SMN/SCH) so we will probably never see any class with multiple jobs again.
Another point against this is that a BLU like this is not just 1 Job with all 3 roles it's 1 job per role or 1 Job per class...to much work even for an expansion...so if we would get this kind of BLU we won't get any other job...

But your idea is good and i like it^^

The reason SMN/SCH failed was it was a different role coming off of the base class which meant it needed different gear, different stats and a different weapon while also having only 5 skills to make it perform its new role. With this idea BLU wouldn't need any of that, it would use the same base class role, stat, weapon, gear and skill set. With its own skills building on what the base class can do. I think of it kind of like the enemy skill materia in ff7. Using their materia they could set themselves up as any "job" they wanted and then put the enemy skill materia on top of that so they're also a BLU. But for this, instead of giving every BLU spell it would only give the ones relevant to the role it is filling.