...And I Persist in "And Another Thinging" Years After the Fact
There is a MDZS fic called The Myrmidon, by Basingstoke It is an AU where Madame Yu successfully convinces Jiang Fengmian to treat Wei Ying as a servant in the name of "protecting him." The Wei Ying we get is not a Super Angsty Woobie, the writer is not going for angst, just (apparently) going for anxiety because a Wei Ying who is a perfectly happy well adjusted servant with no cultivation and no core, who will never be Wei Wuxian, and more importantly, never going to be the Yiling Laozu, is a guaranteed bad end.
The writer does manage to finesse a successful Sunshot Campaign in a believable manner. Probably one of the best aus simply because it doesn't try to "hit the mark" on any point in the canon timeline.
What the writer does not do is convince me that someone is going to revive a very dead Wei Ying however many years after the fact to solve mysteries. First, because Wei Ying is a bodyguard with probably some valet duties thrown in. He wasn't given any kind of advanced training in doing investigations. Second, he is not a cultivator or gentry plus cultivator. No one would listen to a damn thing he said. Third, what exactly needs to be solved? We know how Wei Ying dies, we know Meng Yao is a manipulative ass who finds honesty absolutely impossible. However we ALSO don't have rescued Wen Remnants, Murdered Wen Remnants or Wei Wuxian crazy laughing on a roof after being shot. Because Wei Wuxian and all the situations that lead up to crazy laughing on the roof do not happen. (Because Wei Wuxian does not exist in this timeline.)
Next, there's the attempt at romance. And I say attempt even though there is absolutely no romance, and no reason for there to be. Wei Ying keeps a super low profile with all the other servants, though his advice to Meng Yao definitely raised a death flag. (Because Meng Yao.) He is sexually active in the way a servant may end up being because "young masters," and "consent" in setting like this have never even been within shouting distance of each other.
His only interaction with Lan Wangji is Lan Wangji appearing to be pissy about Jiang Cheng giving his body guard/personal servant a "title." Wei Ying has more chemistry with Nie Huisang in this fic, and Wei Ying very clearly views the relationship as transactional.
(Honestly, the implication that Wei Ying is turning tricks for favors/gifts/money is somewhat worrying because it indicates that his actual situation is slavery and this is the only way he's been paying off his contract, because he isn't being given a salary. On the other hand, maybe it's a side hustle?)
In any case, I do not see how Wei Ying/Lan Wangji could ever be a thing. Wei Ying is not likely to detect anything resembling attraction from Lan Wangji, who as far as he knows, dislikes him. Lan Wangji, seeing that Wei Ying is probably going to marry a Nie cultivator (IIRC), is not going to approach him. Also, Wei Ying is not a cultivator, and therefore, not a potential cultivation partner.
But say Lan Wangji did approach Wei Ying. Is someone going to tell Wei Ying that Lan Wangji is interested in him as something more than a convenient random part time sex worker? Is Wei Ying somehow going to understand he the situation is not transactional? I think the answers here are very much no, and no. Wei Ying instead would be very annoyed, though he'd play it off as "Lan-er-gongzi is so peerless, he can do whatever he pleases," or something flirtatious like that. Whiiiich would probably hurt Lan Wangji's feelings. (So you'd get a one pixel frown.)
I would not (years after the fact) still be having mental arguments if the fic were not that good, and if the story didn't just end with Wei Ying walking out of the special servant graveyard for special Jiang servants.
Aaaauuuugh. How was it supposed to go. I still can't buy Wei Ying/Lan Wangji. How. How.