Well, ok, I'll make a first serious nitpick (hey, I did the same when Rome demo went out and it turned out to be spot on)...
I feel that combat resolution and land units movement is too fast. If 20 days is enough for Italian units, that are mainly infantry to break the Yugoslavian defense (even if YUG were not mobilized at all, ITA was only partially mobilized) and get almost half of YUG territory (mountain terrain, not that high infra), and occupy half of the country, then imagine what can do motorized/mechanized units with proper doctrines, commanders and in easier terrain/better infra.
Of course, I might be wrong, but seems like some tweaking might be needed here and there. Nothing big considering game is not out yet, still, something to think about.
Otherwise, awesome AAR.