So I believe this is the definitive list of what ship types each AI opponent gets:
1) The triangle ships (Fighter, Bomber, Missile Frigate), Mark I-V
2) Any ship types unlocked by their AI type, Mark I-V
3) An additional ship type, Mark I-IV
4) Additional ship types unlocked based on AIP, Mark I-IV
5) Two ships types, Mark V (does not unlock Mark I-IV if that ship type isn't unlocked by points 3 or 4)