Feature: consumable game logs and replays

There can be a wealth of knowledge derived from the game logs. Unfortunately it's not really in a form that is easily consumable. How much effort would it take to produce a log of all the game events as JSON? Also, would it be possible to have this log at both the client and server level?

My use case is applying this to machine learning, and using the past games as kind of a training set. But I'm sure there are other uses.