In the expansion's singleplayer campaign, I played normally until towards the end I felt like doing something differently. It's kinda sad how well it worked:
I bumrushed the enemy with my ACU, taking almost 100% damage but freeing an SCU. I put time compression on and upgraded both to be fit for their maximum combat potential, then rampaged around, destroying various outposts. Eventually I went back to the spot that normally would have been my base, noticing that I was not attacked. At all. I was basically ignored by the large T3 assault base in the corner even though I was stomping around outposts for half an hour. Once at my base spot, I made a huge array of t3 generators and fabricators, shielded it all, and surrounded it by SAM sites, t2 defense, tactical missile defense, and a strategic missile defense building. I didn't even build a factory, and I completely skipped to t3, and I was still getting away with all of it. Eventually I got attacked, but by then I had all of the defenses set up so it mattered not. I never even built engineers; I had an army of SCU's ready to do my bidding. With the Paragon built, I was pumping out Galactic Colossus experimentals every 30 seconds. QAI didn't stand a chance... I laughed at the side quest option to free the galactic colossus on a little island, considering I already had 20 stomping around.
You can do ANYTHING to the AI.
I tried this same tactic on hard, and it was a bit more difficult, but I still managed to do it.