Hello Commanders!
Wanted to jump in and say that we wanted everyone to know that we included Co-Op Mode so that a wider portion of the player base can participate in the "Exeter's Last Stand" missions to possibly earn this ship for free.
One of the main points of contention seems to be "Can I shoot down 30 planes in Co-Op battles?" The answer is yes, but in Co-Op battles, it may take a bit longer, as you are more likely to shoot down Spotter and Catapult planes as opposed to Carrier planes.
For the contention of "I cannot earn the 7 achievements in Co-Op" this is rather true and seems to be an oversight. It will be better caught for next time.
Hope this addresses the major concerns and good luck to all out there to earn this ship!