I had a similar idea just yesterday. Galcom would send messages "suggesting" missions you could undertake, much as you have suggested. But the message they send you would be encrypted; you would need to enter your CD key to decrpyt. Enter the wrong key and you get a different jumbled message than you received.
From the player's perspective it's just another feature with a twist. I wouldn't presume to say what 3000AD's perspective might be but I don't think it's a security liability at all.
Edit:
In fact, I'm here on the forums looking for posts on interesting places to go and do and see. I like the open endedness of the roam campaign but would like to do the occasion mission so I can take a break from conquering the galaxy. Basically, textual missions would be perfect.
