Unlike most people on this thread, who prefer shooting things down first and then ask the questions, i would support the idea of a necromancer job ( also spare me the lorebreaking hipocrisy when AST has Neutral Sect and WHM going full holy magic instead of getting his nature based spells).

IF we would get said job in this game, squeenix would probably design things, as referenced before, on the FF5 Necromancer job and maybe add some spells from Nybeth from PotD into it.
That would mean using either a rod or a dagger, a scythe is imo way too bulky and too cliche for a Mage that has to stay hidden.

As for abilities, since yoshi p. hates pets and properly working jobs in this game, the skills would be maybe kind of like zombies having to charge their target and then blow up when it comes to the oath skills, a good amount of Dots and debuffs to have some qualities in a Party and of course, healing that comes at a price. A Necromancer would, if it ever would get added into this game, be more of a healer/support job, rather than a dps job.