I have some suggestions for troops for all factions but I will name them as this topic unfolds.
The little willie was a pre tank that was used to carry weapons and supplies.
By the way gabbe change the tank pic on the tech tree, its a liberty tank and those were made in the 1920's
The howitzer should be moveable by horse, but here's a suggestion, do not limit it to five units they did not do so much damage, instead make an ammo depot and say that you can have 2-3 howitzers for every one of these, I am implementing this into tech mk2
France should also have a surrender ability
Germany should be very good all around and have the best heavy artillery and two very good late game tanks that I will name later and a captured british tank, their first generation aircraft should also be good, good bombers variety of gas upgrades, submarines.
England should have a great navy as you said, but also the best trained infantry(they could fire 20 rounds a minute with a rifle) and the best all around tanks especially in variety, their airforce could be good late game especially in the navy and bomber section.
Norway should have a great economy, as mentioned, but should also have a good coastal navy and coastal fortifications, ski troops
.
France should good fortifications, though not as great as said, Norway should have better, they should have good late game light tanks but their other tanks should be the worst in the game
, average navy, great light artillery, their 75 millimeter howitzer allowed fire of up to 15 rounds a minute, good late game fighters.
If implemented I will mention the strengths of the russians and italians.