Would be interesting if sites could be grouped based on what services they rely on, or just grouped based on which have correlated downtime.

Correlated downtime and this is a place I wouldn't actually mind a guess from AI on whether their is a common underlying cause between some of the things. I say AI because I don't really think anyone is going to keep all of the possible common dependencies of different privately hosted systems up to date, but AI could at least take an initial guess + try to find if anyone else is posting root cause theories elsewhere at the time and link to those (and a guess is fine enough).