Just make it so the map resets if and when the IJN captures the island of Midway. The captured airfield wouldnt be able to spawn planes at all for the Japanese. They would have to capture all facilities at the island, which hopefully would include an airflield, port and 1 or 2 v bases. Once these four were captured, the map would reset. I dont think fleets should get to respawn either, if there is a way to stop that. Perhaps fleets respawn time should be set so high (if this is possible) that they wouldnt likely respawn before a reset. Thus victory conditions would be:
IJN: capture Midway island.
USN: sink all 4 IJN carriers.
This would be very different from anything done in the CT in the past, but lots of different things have been tried in the CT before. Its only 1 week, why not give it a try.