I imagine an AU where JC secretly saves WQ, gives fake ashes to Jin sect and keeps her hidden in Lotus Pier to become their secret healer.
He hates Wen-dogs but is too prideful to let die someone who saved him and gave him the opportunity to rebuild Jiang sect.
He never clearly tells WQ why he saved her, and only says "You know why I saved you" and that it would be a waste to lose skills that would be useful to his sect. But ofc WQ isn't stupid and knows the real reason.
Jiang Cheng intervenes when Wen Qing and Wen Ning surrender to Jin sect. However JC only manages to save WQ. Saving WN was never among his plans since WN is responsible of the death of Jin Zixuan
For the sake of Jiang sect, JC has to keep WQ hidden. She clearly doesn't like the deal and sometimes tries to escape or thinks of killing herself, but JC dissuades her.
Escaping and revealing her existence could bring troubles for Jiang sect, and she doesn't want that. So she keeps helping Jiang sect with her medical skills in secret.
I don't know how Jiang Cheng deals with the cultivator world yet, but Wen Qing's existence is certainly revealed after Jin Guangshan's death.
Time passes... and JC takes a liking to WQ, some of her personality traits remind him of his mother and it's kinda comforting. He eventually develops feelings for her, even if their respective stubborness causes them to always argue.
Finally, JC is too much of a coward to take a step, but his feelings are obvious enough for WQ to notice and she makes the first move.
I haven't thought of the next part yet, but I got some funny ideas like JC nicknaming her "Princess" after one of his puppies. He keeps calling her that with his serious leader face in front of his subordinates who are like "Huuuh!?" and JC scowls at them like "Got a problem!?"
And that's all for the moment. Thanks @Patallyry for helping me edit the text of this thread.