You sure you didn't mean to refer to that as how you Do Fandom Right? Because that is doing fandom right. *off to check your AO3*

I go out of my way to make writing origfic a shared thing, actually! It helps if it's mythfic, of course, for obvious reasons, but you *can* do that with any origfic if you're open enough about it from early enough in the process. (Which means from the idea stage, or very, very early in the first draft. Or zero draft. Whichever.)