Depicting a single regiment would be problematic in terms of game scale. In general terms, a game on the scale of Global 1940 represents (admittedly in very abstract terms) the actions of units that are mostly the size of army groups and fleets – and, furthermore, of army groups and fleets which have no specific identity other than their nationality. It would be hard to justify saying that one particular regiment-sized unit, with a specific name, ought to be added to the game; by that rationale, there are hundreds of other regiments that could be added too.
The obvious exception to the above principle is the single fighter which represents the Flying Tiger squadron in China…so it’s not an ironclad rule that units smaller than army groups and fleets are never represented in the game. It can be argued, however, that the Flying Tigers are a special case because of their high profile, and because in the game China lacks aviation forces of its own. China doesn’t lack infantry, however, so adding a USMC unit doesn’t bring anything distinctive to China’s forces.
Additionally, Global 1940 has no rules that govern riverine operations – which is understandable, because the game map doesn’t depict any rivers. Even the Saint Lawrence, which is huge in real life, isn’t depicted: on the map, it looks like a strip of land. There are a few lakes depicted, plus a few canals and narrow straights, but no rivers. So a river patrol unit in China would literally have nowhere to go.
If you just using A&A Pacific, 1940 (2nd Edit.) as a “Stand Alone” game only, and using this as a “Special House Rule” scenario it wouldn’t be problematic and would make this interesting for the folllowing reasons - By the rulebook, the U.S. and Japan are not a war yet until Japan attacks first (which would be stupid to do outright) and if this is played in the “House Rules”, Japan may place their all of their units in the Sea and Land zone of Kiangsu Province. HOWEVER, they DO NOT recieve the IPC for it until either ALL American Forces in China (the 4th Marine Regiment and the Yangtze River Patrol at Shanghai) are either evacuated out of China and headed towards either the Philippine Islands (which both actually did do in 1941) or eastward towards Hawaii or one of the outlaying Island outposts before war is declared or Japan decides to “sneak attack” and goes after the American Forces in China and wins, that is when they finally recieve the IPC for the Province. Until then NOTHING, it would be a “Eyeball to Eyeball” scenario in the “Special House Rules” to see who blinks first. And thanks for reminding me about the AVG (the Flying Tigers") in China, i will definitely add them in the “House Rules” as well.