Great post! I've only recently been getting into point processes and it's nice to see it applied on a real world application that is also easily understandable.

I think that non-baseball related injuries can also be incorporated as external events that have their own additive influence term in the intensity equation that decays with time, if there are enough such data points to justify it. I've seen this done in some (finance related) paper, but not sure how it affects the likelihood calculation.

Also, I'm not familiar with this field. Is your accuracy typically what can be expected from other ML models too?