Just a speculative poll.
Third is keeping players playing after they have figured out the UI. This is where an AI that behaves more realistically is important. It gives feedback to the player. It also establishes a norm of conduct for interactions in the game that will bleed over into PvP interactions. Whether we intend to or not, we always will include examples of modeled behavior in our list of options we might do. If the AI is modeling accepting war goals short of total surrender, the PvP interaction will start to include that also.