I believe the generic focus tree has a path towards joining the main factions which the Netherlands will get.
You don't need some special Dutch focus tree for any of this. If you want to suck up to Germany then spend your PP to improve relations with them, using the diplomatic options. If you want to be a fascist, appoint a fascist minister, so support for fascism increases. If you want to fortify your provinces to defend along the New Holland Water Line then use your civilian factories to construct forts. If you want to re-arm use your military factories to produce the equipment for new Divs and air wings.
You can't "buy" tanks from Germany. The only way German tanks will be in the Netherlands is if they roll through Benelux on their way to Paris, unless you can join the Axis or you play in MP and have a very generous German player who decides that it would be useful to keep a neutral Netherlands that will trade them resources from DEI
The focus tree just provides a guide to different strategies, with some useful bonuses. So if you want to re-arm like mad then you might take a branch that improves your industry, or if you intend to go into exile and try to defend DEI then take a focus that improves your navy, and build as many factories/dockyards as you can in DEI rather than in Europe.
Yes, I'm saying, that other than for flavour reasons, everything you want should be possible using the standard mechanics of the game, plus the generic focus tree. UK has a focus for the Shadow Factory Scheme, but everyone can disperse their industry to protect it from bombing. Japan has a focus to Increase Naval Production, everyone can build more dockyards if they have coastal states, empty buildings slots and enough spare consumer factories. Germany has a focus for the West Wall, but everyone can fortify their provinces if they have enough spare consumer factories.It might be that I'm misunderstanding you but are you saying that a National Focus tree for the Netherlands in general is redundant or are you saying that the options I provided so far are 'redundant'? If the first thing is the case then I'd say the more 'flavor' options the better. Even if most parts of the Dutch tree are the generic tree with renamed options it would still be better than just a generic tree with generic options.