Sorry for joining this thread a little late, so here's all my responses bundled up:
It should be relatively easy to let the game give an auto-response of "No human players saw your message" (and possibly, "No human players still in the game saw your message"). How useful this is would be another question of course.
I'm unsure whether it's a good idea to allow controlling AIs. In a 3+ players per team game, both players could give conflicting orders. And you'd have to be able to cancel orders. And maybe you want to move your own armies out of Peru first, so it would have to become "attack at the end of your turn". And let's add an importance indicator; maybe the AI has no armies currently able to attack Peru so it would have to use two reinforcements in (let's say) Brazil that it really needed very badly somewhere else. Writing an AI is difficult enough [Frankly, I'm amazed at how well it plays. Sure, it makes stupid decisions every once in a while, but for a one-man project...? I have no illusion how long any AI I'd ever write would survive against the actual WL AI, let alone against a human player.] and adding even more complications onto it sounds like a bad idea to me.
And by the way, from what I've understood, in this situation, it's not even needed, here's a quote from Fizzer in the "[treat teammates as enemy... default?](http://warlight.net/Forum/Thread.aspx?ThreadID=2489
|> [The AI] will attack teammates in some circumstances, [..]
|> It will only attack teammates in two circumstances. First, if a bonus is entirely
|> controlled by teammates and it has >= 50% of the territories, and it will only do
|> attacks of 2.