I'm afraid I'm really too busy to cowrite a fic now, especially one I don't know much about. Got exams and also a uni project to work on during a year, on top of other projects I'm working on (e.g. own writing projects including a fic and articles, helping with the upcoming GT, etc). I can help beta read or bounce ideas off, no worries there, but not write.
Pity to the people with flat feet, I suppose.