Why would it not be fun? I understand they may not have a lot of the architecture that many FPS games really rely on but I'd think the jungle environment would be pretty fun. Somewhat similar to a few parts of the Japanese maps in COD:WaW. Maybe a level or two with a big area covered by those merchant boats they have. And though most of the depicted warfare of Vietnam was in the jungle they do have cities that could easily be used for great maps.