They could have BLU as a class, and branch off into 3 different jobs with different roles. that way you can pick whatever role you want at any time, without dumping everything into 1 job.
ACN can fill any role basically...can heal, can use tank pet, and be DD. So there's no reason they couldn't do that with BLU, also.
Sure ACN is a bit OP at lower levels, but at end-game, not so much.