I've always been in favour of the class+split-jobs system, so it's sad to see them turn against that.

Honestly, classes are the better-designed facet of the game to me as it is (and when cross-class skills were a thing, even more-so) while jobs just felt tacked on and many of them just seem... off, for lack of a better term...
Flipping the roles of Thaumaturge and Conjurer way-back-when simply to have them go to Black Mage and White Mage respectively wasn't cool either, IMO, but whatever. :-/

Granted, the whole Arcanist->Scholar/Summoner was kind of wonky from the get-go, but Arcanist at its core just seems kind of random and poorly-thought-out to me (with Summoner and Scholar being the most 'forced' of all evolving jobs on top of that).
Lorewise, I'm not sure why the Biomancy angle was even there, and even the carbuncle summon was more like a "Naturally, our studies lead to the summoning of Carbuncle... Naturally" kind of justification than anything that actually seemed... well... natural.
The current lore would seem to lend itself more to an AoE trap-master style of gameplay to me, but eh...
Disregarding that though, I still say that arcanist should have been split from the start with both splits getting branching jobs.
1) Take the biomancy half and build a class around that, then evolve it into Scholar (ideally with a plague-doctor motif) and and DoT-heavy 'plague-bringer' kind of class.
2) Take the summoning half and build a class around that, then evolve it into a proper summoner, and possibly a new take on Blue Mage (Summoner could be like Ellen from Folklore, while Blue Mage could be more like Keats).

If we did get continue with classes and split jobs though, we could have had
1) A proper gunner/musketeer that could become a machinist or a sniper (still salty about this one. Musketeers already had a damned guild!)
2) Archer could split into Bard or Ranger (though with better foresight, the whole Archer->Bard thing could have been avoided too)
3) Necromancer could be an alternate path to white mage (And I still say both should have come from Thaumaturge, but eh...) Ship's already sailed here though, TBH. They wasted the character best suited to being the teacher here.
4) We could have had advanced jobs where Red Mage was actually unlocked by progressing to a certain point with White Mage and Black Mage.

Basically, I'd say we should start over and retcon everything that's already been shoved into the lore about them so classes and jobs can make more sense. >_>
Which isn't going to happen, granted, so at least it would be nice to see new classes/jobs/splits handled well rather than abandoning the core basis of it because they didn't handle Arcanist properly (and because they don't want to make anyone start at level 1 again).