What about a set of older games? 7 Years War, Napoleonic War, US Civil War? Each board game would have a different market, with the 7 years war being the most ‘global’ of the 3. I cant imagine the US would want to see a Napoleanic War any more than Europe would be interested in a US Civil War. Maybe an game for the Asian market also but my knowledge of vast Asian conflicts is sadly lacking. Moving further into the past (which to a certain extent includes WWI) will only make the games more and more regional, so a set to cater for all markets.
All 3 conflicts listed here however, were fought over vast areas and could have good strategic possibilities, and all 3 could use ‘similar’ styles considering the the methods of warfare probably changed less between mid-1700’s and mid-1800s than they did between 1914 and 1945.