I don't even think that would be necessary, given the whole Library-esque nature of Blue Magic... You'd just choose the spells according to the content you're running. If it's a dungeon run, maybe worth to put a Bad Breath or a Mind Blast to help with paralyze on trash... Raids, maybe not.
The cool thing about BLU battle design is that you don't necessarily have to fill all the spell slots with rotational abilities to be able to fully perform your role; you have sort of 1/4 of the spellbook kind of free to add whatever situational you think you'd need.
Come to think of it, if BLU would ever become a mainstream job, this would possibly be the only thing to make it stand out:
- Being able to choose your rotational spell "skins", since you have options to which "astral 200 potency spell" you can bring;
- Being able to customize the utility of the job, given this 1/4 of vacant action bar. It would also put BLU in the "support dps" role like Dancer, Bard and Red Mage
