I think that more fanfiction should be written with the aim to tackle the original meaning of hanahaki. Because when the concept of hanahaki disease was originally created, it was intended to be a metaphor for suppressing one’s feelings.
Your feelings are this beautiful garden of flora inside of your chest. When you express how you feel honestly, you allow for it to grow freely. But when you hide how you feel out of fear of rejection, and try to make it smaller and smaller, the flowers become cramped inside of you, until you choke on your own feelings. Every flower you cough up is something you’ve felt, but refused to say.
The whole “dying” thing is intended to be more symbolic especially. You’re killing off bits and pieces of yourself and how you feel, because you’re afraid to express yourself.
It’s not really supposed to be, “The one I love doesn’t love me back, and I’m dying from it.” Rather, it’s more along the lines of, “Repressing your emotions is bad for you, and it’s better and healthier to express them freely, even when it’s scary.”
Which is to say that, one, the cure for the disease should be telling the person that you are in love with how you feel. How the other person feels about the person afflicted should have nothing to do with it, as the trope is meant to be about feeling your emotions unapologetically.
And that, two, it’s not an inherently romantic trope. Obviously, it has romantic applications, but it can be written for any situation where a character is hiding how they truly feel. This can include a refusal to address a specific trauma, a desire to indulge in something that they’re ashamed of, and even really practical things, like wanting to ask one’s boss for a higher position.
Although (as an aromantic person myself) I don’t agree with this conclusion about the trope, this application would also avoid people calling it arophobic. When the thing killing the character is a refusal to be honest with themselves, rather than an unrequited love, it’s on nobody’s hands but their own to save their life.
There are a ton of ways that this interpretation of the hanahaki disease could be applied in new and interesting ways in fanfiction, and I’d love to read what things people could come up with!