From: Chicago, Illinois
My opinion would be for scenario 1---->
IMO anything on the outside defensive perimeter in the Phillipines is fair game. North coast of Borneo from Kuching heading east as well . I'm with the same that view south of Khota on the first turn in Malaya and DEI should be off limits.
Here's my resoning for the Phillipines and north coast of Borneo or even Guam.. What's the time differnce from Pearl to Phillipines 8 hours? I believe if the Japanese Empire wanted to attack anything on the outside perimeter of British North Borneo or the Philipines there was little to nothing that could have been done about it. Since the lynchpin of everything --> the Pearl Harbor operation happened well in advance there was no fear of any moves tipping off an attack at Pearl.
Moving forward--- both sides benefit from hindsight there is no reason to handcuff Japan as once the Allies get the initiative Japan will get brutalized in part because of the the pace of operations (both sides benefit from), the ability this game provides to supply and knowledge both players have of the other sides forces among others.
For scenario 2 AARs where I you'll see Marines in Burma, the DEI, Indians, British, ANZAC in Japan , if the Allied comander isn't going to play with historical restraint any attack should be fair game.
I tend to agree with you Sulu Sea. A convoy in the South China Sea heading south from Saigon would have raised significant alarms, but the Allies were already on high alert, as they spotted a ton of shipping in the Gulf of Siam on D-1. The only possible "what if" is what if Force Z had decided to sail for Brunei when convoys were spotted in South China Sea? Were they ready to do that even on D-1? Allies also didn't have much recon over S. China Sea as opposed to Gulf of Siam, so it's possible that shipping would not be spotted. RAF was keeping an eye on Gulf of Siam, for sure.