I second what Mucca said about the potential being there to tie it up as a shorter story if you want, and while I totally understand the difficulty in staying motivated when no one else is interested in your story (or sometimes even when they are ;P) I think you'd be surprised at the kind of reception you might get for some of those more niche pairings. Like the scope may not be as broad but there will be people who are super onboard and never get to see that kind of content who'll be super excited to read it.

TL;DR - You can do it boo!