Six still might be too much. I could live with maybe 2 or 3: Evita Peron for Argentina, Gandhi for India (as long as we have others as well), and I guess if Australia comes back, they will need one as well. Though I guess 19th century Henry Parkes could work for them.
I was trying to think of any WWII European leader, similar to how the Dutch got Wilhelmina this time, which I didn't mind her inclusion for this game, at least but couldn't think of any I really would want. I still don't see Churchill or de Gaulle as compelling as their earlier counterparts. And I'm not about to pick Germany, Russia, or Italy for that category.