It annoyed me too, that you can't do something the AI tells you to do, and I couldn't fathom just which Tech you'd have to research to enable 'Advanced Espionage' (Xeno Ethics, perhaps?).
So I resigned myself to Trading with them; and then building up my Diplomacy skills to the max so that I can rob them blind of money and bolster my Influence points by trading Techs that they probably won't use or trade-on. Or sometimes I just invade and add that nice, juicy 15PQ point planet to my colonies. I'm still learning on my first game in V1.0, so I'm hoping that the AI will add more "minors" on the hoof to replenish the stock as GC1 tended to do. On balance the game is better with the "minors", as at least in 'sandbox mode', they do not hog the Galatic Trade items (Frictionless Clothing, et al). Perhaps when I feel I've graduated ready for the full campaign and play that I'll find them a tougher prospect.
