Since AIs don't have any turrets as of Unity, they've lost a major attribute and specialization. Theoretically, yeah, mobile ships and guardians will replace those, but offensive types obviously use those too, and they'll all just behave as normal ships once you get their attention by destroying the command station or attacking a guardian. Effectively, instead of waves, they're becoming more like any other AI, though through CPAs after you provoke them, theoretically.
Are there any plans on diversifying these AI types? Any AI-specific hindering structures or ships, or some special behavior type of some sort?