gulopine
While building https://foauth.org/, I had wondered if it'd be possible to do something like this, but it wasn't really my use case so I didn't really pursue it. I was more interested in people just trying to get access to their own data, so I built a solution for that side of things.
Still, I can speak from experience that wrangling 50+ OAuth providers into a single system is hard enough, and trying to provide a unified API to all of them is even harder. I'm not sure how many sites need to support that many sites, but for people like us trying to simplify the API for others, it becomes a pretty big necessity. As it is, https://github.com/gulopine/foauth.org/tree/master/services is something of a living tribute to the differences between the various service providers.
So yeah, I'll be very interested to see where OAuth.io goes, and for anybody else here who just wants to get their own data (but not run your own service), you might also want to checkout https://foauth.org/.