In the end this is what I think too.
If you make the dungeon important, which I think we all agree doesn't have to be, and say there exists a strong relationship between the jobs such that we would never see Berserker cause we've already warrior then:
Berserker -> Warrior
Thief -> Ninja
Necromancer -> ?
Summoner someone might say but I hardly got those vibes (may use ink mage to further distance that), unlike I could see clearly where berserker and thief were lining up from. Though I wouldn't die on that hill if someone was willing to die on the hill that necromancer was somehow summoner's mirror lol. As ultimately even if the boss means nothing you've still the entire good guy soul magic that is also teaching another.
The reason why I think this is relevant, and I've seen you said so we're really just choir agreeing now lol, is that the entire freaking expansion has had relationship to soul magic, and there is actually a character going out of their way to learn it, and on top of souls clearly being in the wheelhouse of necromancer (being very literally part of their general /non/gamer specific definition) that then there is this guy who looks kinda evil like when in battle mode.
I would toss my gil into the likelyhood that the mirror of necromancer is that dude over any other job we've got.
This also plays perfectly with providing a necromancer like theme'd job while also not taking a huge jump into the piranha infested waters of summoning skeletons (which is why I suggested when I made my dark healer thread, avoiding the human corpse enslavement). I still believe if you tried ridiculously hard and did things like shade beasts, using the blood of monsters only, with the use willing souls (this can be both malevolent and benevolent) and your own creation magic to create 'undead / undead' like apparitions- that you could get hyper close to necromancer without breaking lore AND without having to double censor yourself for China, to the point any foreign person to the game would see the job and say "yo, that's a necromancer", but man you're really trying at that point. Although I do enjoy coming up with those ideas lol- still my point of putting in that creative work was just to argue being creative and trying hard can move entire seas and mountains (without breaking lore), of course it only makes sense to try hard if it'll be worth it / fun (which is where I guess I can see some people holding tightly to the game and saying "NO GET BACK STAY AWAY" lol, but at least I hope wherever possible to see more creative communication and less walls for the sake of preventing something).
I suppose people worry about others running around a chainsaw near the lore, but seeing as I've guessed (more likely) and or helped influence (less likely but possible) a few direction shifts in the lore already I feel like I'm at least half capable of emulating what seems logically plausible. (SMN, Beast Race, Beast Tribe, Job progression, I've done a fairly decent job on getting close enough they read very similarly, which either makes me believe SE absolutely listens to feedback regularly or I'm this forums budget Nostradamus, heck even on non-related content like SE response would be for the two races (Viera / Hrothgar).. I had did fairly close emulation of what would be said /done. Not saying I'm perfect but hopefully people might think to trust I'm not going to purposefully take a huge dump on their game, and am not completely unhinged, because it's 'my game' too lol.
Like if we're being serious, soul mage has been more discussed and exampled MORE than chemist. Because soul magic has been of massive import for basically the entire expansion, and shown as a learnable skill as well (so it's not just 'fae magic only'). And in relevance to the discussion beyond using "google defines necromancer to commune with the dead and spirits" is that the soul mage did have a very evil / dark magic vibe when in their battle format.
On top of that one of the favored jobs story of this game is dark knight, and the most popular expansion also is playing with dark and chaotic things (for much of the expansion there is an exceptional burden)- that this makes something necromancer-adjacent seem possible to me, as necromancer could continue what has proven to be popular concepts. And like I said before while I wouldn't gamble on my suggestion of getting hyper close to necromancer, I would gamble a little bit on a soul magic job that was FFXIV's response to players wanting something dark and something necro related. I only put so much thought into ways to make it happen as I don't appreciate conversations being obstructed due to overconfidence, much rather swim in the unprotected dangerous waters and hit a few sharks on accident and SE if they liked what they saw would perfect it up before going forward (I have faith SE both cares of feedback but also the mind not implement the most wackadoodle idea someone came up with 1:1, they'll only be inspired rather).
Not that it has to be that fae's job even, just if we're sitting here arguing references that fae is worth pointing out as they've far more presence than chemist does (and a fairly easily arguable relationship to necromancer, but in a more positive light obviously). Not that I'm discounting chemist.
Their Oath skill is more like Ranger's skill than a Summoners though, since they had a pet but also then had a lot of other side magics. Maybe I would call them a unique dark element theme'd black mage with a dark element ranger pet lol. Although what I find more likely that FFV reborn is that they're going to make something new, well if they were going to do something at all, in which case it's a brand new frontier.
https://finalfantasy.fandom.com/wiki...Fantasy_V_job)
They actually have quite a few pretty neat skills. Their ultimate makes them turn undead like a Lich.