Show me the person who doesn't want the "Masked Carnival". You'll be hard-pressed to find them. That is because most people don't mind it, if they don't actually share your enthusiasm for it. Like you said, it's different, it's fresh, and it's loyal to the job in certain ways.
But this is an MMO. When people ask for jobs in this sort of game, they want to play it in the main content. They want to be able to raid with it if that's what they fancy, they want to be able to run dungeons with it, they want to be able to run MSQ with it. They want to main it.
I personally want to walk up to Zenos with Hien and the Scions at my back and imagine their reactions when my next move is Bad Breath. It doesn't seem like I'll be able to do that.

As others can say better than I, XIV is no stranger to tweaking jobs so it fits in with its system, even at costs to their lore. Having a version of BLU that will be usable outside of its personal grind and Masked Carnival is far from being mutually exclusive with it being this new game-mode.
Yes, we need more innovation. Yes, we need freshness. But to introduce a job, one that was so highly requested, and to limit it to this is... meh.