Here is a little info on Denmark during the occupation 1940-1945:
Oil & raw materials = Nothing that I know of.
Agriculture = Some historians have concluded that Denmark in 1940-1944 supplied 10% of all Germany's food supplies, and 1944-1945 15%.
Industry: 20% of everything produced was exported to Germany.
Loyal population: Well in the start of the war, the population was pretty much unaffected by the war. A bit upset about being occupied, but most people agreed that it was better than having Europe being overtaken by Communism. Denmark resisted with its military for a couple of hours and lost about 15-20 servicemen, while taking out about 20-200 germans. The government and king surrendered and Denmark was spared of any destruction during the war. Denmark delivered more SS troops than resistance fighters, but more importantly the government, labour unions, fishermen, farmers and industry were more than willing to cooperate with the Germans, make money and get through the war relativity painless. Most people who had anything to say was pretty anti-soviet, but split between supporting UK or Germany. Most thought and expected Hitler to win the war, up until 1943 when the war luck changed.
A critical crossroad: Well, I think it was a critical naval choke point and many supplies to/from Norway went through Denmark by ship and train.
Important harbours: Aalborg Airport was the most important airport as it was a stepping stone to Norway (the primary target of the German occupation. Denmark was just kind of "in the way"). Frederikshavn was also an important harbour linking supply lines from Norway to Denmark. Of course also Ålborg/Aalborg and Copenhagen were important harbour.
Terrain/climate: Denmark is very flat, full of farmland, has a lot of roads but is also composed of islands, relatively easy accessible.