I was thinking more along the lines of, "Oh, yeah, Scholar. In for launch, you say? Good idea. Oh, and incidentally it would also make less arcanists running around!" That seems a more logical progression for the hypothetical conversation to have taken. You watch. The big reveal tomorrow will be that Thieves wear mortar boards and carry books. Stolen books.
MSK -> SCH. The sound of all my Corsair dreams dying would be audible. As for two jobs/one grind, that's sort of my main objection. I don't want a level 50 job I haven't touched.
Besides, with ACN/SMN being confirmed as primarily a DoT job, that still leaves a niche for the more traditional enfeebles (though that might be stepping on the toes of a potential RDM a little). Not to mention the interesting non-combat abilities SCH (/secretary) has had in the past. I'd love to know the actual HP on some of these mobs. Libra me up.
I don't think any other job is really "necessary" at the moment. All core party functions are covered. But I'd love to see more, as would pretty much the entire player base, so why not start with scholar if a forth full mage was the way they wanted to go?
Edit: (I seem to be typing very slowly today)
In... I think the anniversary presentation? In some announcement, I'll hunt the source for you in a minute, Arcanist was confirmed as specializing in DoTs, with Carby having a "casting" and a "tanking" stance. That's all we know about that. But that does appear to still leave buffing, crowd control, and the non-DoT enfeebles up for grabs.
Editedit:
Mm, looks like I was wrong and Arcanist is mentioned as having regular debuffs as well. Which still definitely leaves buffing and possibly leaves crowd control free:
The top part says it's a pet class, below that is listed the types of magic it is proficient with (HP reduction through DoT and weakening enemies through debuffs), then the bottom part mentions Carbuncle and you can obviously read the English for what it has to say about him.