I think the main things you could base a Netherlands tree (or modification to the standard tree) might be options for improving their colonies and navy, or building fortifications within the Netherlands itself. The Dutch East Indies were a major target for Japan.
The only real problem is that it's pretty tough to find "high points" in the Dutch experience of WW2. On land the Germans and Japanese pretty much demolished them, and their surface fleet got virtually annihilated by Japan.
The best I can find is Conrad "ship-a-day" Helfrich, whose submarine force destroyed more Japanese ships in the first weeks of the war than the British and American navies combined. On the other hand he was in charge of the Battle of the Java Sea, which is a poster-child for "Japanese torpedoes are really deadly".
Although it is true that The Netherlands were not in the best shape for a war with majors like Germany and Japan (abysmal shape might be a better term to describe the state of the Dutch army) they did manage to score some victories. 'Ship-a-day' Helfrich is one of those examples but another 'significant' one which I would like to point out is the destruction of a huge amount of German transport planes during the German invasion of The Netherlands. In fact, 278 Ju 52's were lost on May 10th alone, thus rendering almost a year's worth of production useless. Although it is speculation, it is said that the decision not to directly invade Great Britain was heavily influenced by these transport losses.
A funny sidenote about how the Dutch managed to score these kills is that my Grandpa used to tell me about the Dutch 'cycling-grenade squads'. The German transports had to land in the countryside because of a lack of fuel etc. The battle was still waging on and not all airports were firmly in German hands yet so some of them decided to land in polders, unprotected from the advancing German troops. Dutch troops would then respond by going to these transports on bicycles with grenade filled baskets and throw them into the planes, destroying them. The historical accuracy of this account is of course debatable, (in fact by far most planes got destroyed by effective AA and German tactical mistakes like landing in marshy areas which couldn't support the plane's weight) but it is still a cool little footnote regarding the German transport plane losses.
Now about a Dutch National Focus tree:
- I'd suggest something along the line of improving the New Hollandic Waterline to hold off a potential German Invasion
- A rearmament tree where the Dutch can choose between buying arms from Germany (thus improving relations or something like that) or Allied countries. (In real life the Dutch were very, very late to the party when it came to rearmament and they made the mistake of placing alot of their orders in Germany. Suffice it to say that those orders never got delivered. Or you can say that the Germans took the liberty to bring the Dutch orders in themselves ;p)
- A naval tree where the Dutch focus on improving their navy to counter, in particular, the Japanese threat. This tree can merge into an ABDACOM tree. On december 28th 1941 the Dutch formed the American-British-Dutch-Australian Command together with the other listed countries after the Japanese attack on Pearl Harbor in order to protect their interests in the region. The cooperation ultimately failed but we are dealing with an 'alternate universe' here, who knows what the coalition could do in your campaign?
- Decisions about colonies and Benelux cooperation or subjugation (The latter is obviously alternate history because that was pretty much a no-go for real life Netherlands. Might fit in an Axis oriented decision-tree.)
-A neutrality oriented tree where you try to be friendly with everyone and trade your way to victory. (Im not sure how to implement this given the game's current mechanics. It seems to be a boring tree although it of course resembles the actual Dutch plan of staying neutral). Therefore it atleast deserves a mention.
Might think of more options later.