Hi,
I don't know whether it is a bug or a game type that we can select CPU players only. Indeed when I close the Human item in the menu, it appears in the previous (or available) dropdown menu, which means I cannot start the game without the Human player. Actually it will be interesting to watch AI vs AI.
To play without Human, you can close all menu items at first and select CPU and CPU only (may be a bug?). What is surprising at that game is Human player is automatically assigned to the 1st player and while the CPU's playing you have the ability to intervene it. That is, CPU and Human players play the same faction collaboratively. However CPU's commands are dominant and the Human player is less effective.
Are all these planned or do you plan a game type such as Human vs Human or AI vs AI, etc.?
Best wishes,
Ali