To add some strategy to the game let's add some mechanics to the regional warfare.
In Hearts of Iron you can attack a Region from multiple locations and it increases you chances of winning. So Let's say Nation A has three Regions boarding Nation B's Region that is targeted. Nation A Get's a +6% Damage Bonus (MPP's don't get this Multiplier). Let's say Nation C is Nation A's Ally and he also boarders the land mass, this would add half of the damage Multiplier for a total of +7% Damage.
The Defender could get a Damage Modifier as well in the case of over seas invasions.
Somethings gotta change though currently there is little mechanical strategy in the game, just VISA Cards.