As I mentioned on @micromatt, I'm working on some new obscure @write_as features tonight.
Right now, it's custom redirects (like what you can do on Ghost). I wasn't sure how I was gonna load dynamic routes at runtime, but it seems I might be on the right path.
This instance is only for A Bunch Tell projects.
Success. Thought this wasn't going to work with multiple users too, but I found a way.
Now when the app starts up, we load all custom redirects from all blogs, and add a custom route for each blog that checks against all patterns for that blog.