Finland is easily the most important of the Nordic countries to get a focus tree, considering the stature (as a minor nation) of its role in WW2 (compared with other minor nations). Norway is the second, and (with no offence to their nationals) Sweden and Denmark a distant third. Having said that, I think all three will get individual trees eventually. The question is how to group the four (then) independent Nordic states.
There could very likely be new "gimmicks" when new packs of countries get released; such as the border wars of the Chinese Warlord states, the license manufacture of the Central European states, the updated puppet functionalities of the British Commonwealth etc.
So therefore I think it would make sense to think are there "gimmicks" that you could apply to these in common?
My idea is to keep the three Scandi countries together, perhaps add some odd bird in there - Ireland? Belgium - another deserving inclusion for a focus tree BTW! - and the "Neutrality" gimmick. Give them decisions etc. to balance between nations engaged in warfare (Sweden has the most historical opportunities here, but Norway has the early war maritime minelaying and captive soldiers etc.), and perhaps collaboration decisions should they get conquered? Ireland would fit the balancing act Neutrality theme as well. The challenge is to make that exciting for the player... Perhaps an additional Diplomacy rework focus?
For Finland, I would group her with Soviet rework (maybe Italy as well), perhaps the Baltics as well? Their war efforts are tied together. As different as these countries are, I am thinking maybe of the air rework here? Kind of an aircraft builder similar to the ship builder from MTG? Soviets had some legendary airplanes with large amount of variants that vary from the standard baseline quite a bit (IL-2, the Flying Tank for example. Both it and the Stuka are CAS aircraft but quite different. There was also even a torpedo bomber variant...) Finns had actually a pretty great little air force, and though they never did truly win air superiority over the Russians, they performed great feats with several models other nations considered lemons. Fun fact: the highest scoring non-German ace was a Finn... And this would also fit Italy I think, they had some good airplane models (also some terrible dogs). Would be fun to model all those three engine bombers etc.
Naturally, the tank builder rework would fit Soviets even better, but Finns and Italians didn't really shine with those things and I'm thinking collective themes here...
