A Real Killer EU2
As a long (as in really, really long) time computer strategy gamer, there is one thing that would really tease my appetite:
Same darn little improved EU
and
Battle mode as in EOA's Shogun: Total War
I'd go nuts for that one. Already when shogun appeared I imagined shredding catholics at Breitenfelt or a last hurrah at Poltava.
The shogun engine already included cavalry, pikemen and muskets, so small upgrades

(cannons like "the Hog" with >200 pound cannonballs) would be sufficient.
In the age concerned, armies were lead from the front (except for Blücher

), so will you please, please just think about it?
The STW platform stability wouldn't hurt, either.

Of course the multiplayer game would maybe suffer (who wants to wait for two jugheads fighting it out on the steppes of Russia) but that's a challenge for the developer.
Anyway, a king couldn't concentrate on several things at once. When you are fighting in Vienna, you have absolutely no clue what is going on back home in Moscow.

Just had a brilliant

idea!
What if several players could team up and play as different commanders for the same country. With real skill/morale/fame/honor improvements/losses resulting from the battles.
ARRGGGHHH
Already playing it in my mind....
Now I know what has been missing from my life until now. Or, more exactly, until that game emerges.
ps. field fortifications would need to be included, though