if I were writing a KPDH sequel I wouldn't focus on ground we've already covered in the first movie, I would focus on advancing to new ground. no bringing back jinu, no redemption arc for the saja boys, nothing like that. so, what would I do?
I'd expand on the central conflict and themes by making rumi's demon heritage a problem in a new way. in the first one the conflict was her lack of acceptance of herself, now let's do one about her lack of acceptance from others. how do we do that?
we introduce another group of hunters.
they can't be the only ones doing this in the world, right? maybe it's another band from a different country, maybe it's some librarians, maybe it's the lawn care professional demon hunters from kentucky, it could be anything. at first huntr/x is thrilled; another gang of wacky people to fight demons with!
except rumi is a demon, one who destroyed the honmoon. she's a threat that needs to be taken down down down.
now huntr/x has to fight to defend rumi and maybe change some minds about not judging people for immutable things about them. huntr/x has a new perspective on demons after accepting rumi AND seeing jinu sacrifice himself against gwi-ma, and they can follow up on one of the most important and overlooked moment of the movie: when rumi asks the demon if gwi-ma is making them do this.
gwi-ma whispers messages of hate into the rival hunters' ears. mira and zoe can get some expansion on their insecurities, motivations, and familial styles as they adjust to being on the hunted end of the equation. they could walk away at any time, and rumi has to know that, and that tension is a GREAT springboard to explore and expand on the themes of the first movie.
and just think of how hard the songs will slap from the perspective of a group forced to defend their right to exist against people who should be their allies.
can't imagine those themes being relevant today.