+1A modern game would not be a "war game" primarily at all. This is one of the least violent times in history. Why is everybody so fixed on the idea of world conquests that would just end in massive coalitions and/or MAD?
Grand strategy games past '45 can not be a military grand strategy game, it's too politically driven, by nuclear necessity. It is not HoI, no matter the features and improvements. Hearts of Iron is about armor, infantry, divisions, mostly conventional warfare, regional strategies, and the means of facilitating them. The only way you get that in the modern area is in very limited war theaters, where MAD isn't a factor.
I feel the only way to expand HoI is through alternate realities similar to the WWII era, or by going back in time. If its not within those parameters, it's a different sort of game, with a different name.