It can work, but they would simplify it so much that people would complain that it doesn't feel like a blue mage, plus it would become the most flexible class, having all three roles in one single class.
It could work by either branching one class into three different jobs (one for each role) or one job and three stances that switches between roles, the first is most likely to happen as they wouldn't have to change the current system, for the second they would have to re-write the whole system just for Blue Mage.
How would they simplify it? Pretty much like Arcanist, pre 30 it would be a DPS, so you would only get DPS skills and maybe a base heal (no tanking skills due to balance), learning tanking, healing and advanced dps skills would come from quests rather than going out there hunting, because they have to ensure (hand-hold) that people will get all available skills so they are not excluded from any content. Role would be determined by job crystal, all skills not akin to that job crystal would be unusable.
What would we have in the end? Not a blue mage, but pretty much a carbon copy of the current classes (or an arcanist with tanking skills and without summon)
