Ok, @zach just convinced me in person that this might be a good idea.

The person can still be a calendar if it’s going to be only one person and a single calendar. But you could also have a dedicated pubkey for a calendar. Clients can subscribe to calendar event kinds rather than need to first subscribe to a calendar list, then to the calendar events within that list. It simplifies the number of queries you need to make to get a list of calendar events. And also, clients can still opt into supporting calendar lists if they wanted to.