Quite an ambitious plan indeed. Germany's crave for colonies was a primary reason for their support of the Boers during the Boer Wars against the British empire.
That being said, it is quite common for militaries to make war plans even if they never expect to use them. For example, the Schlieffen Plan of invading France was made decades before it was used. I'll let you in on a little secret, von Schlieffen was quite dead by the time the war started. Also the French knew the contents of the plan since at least the previous decade.
Another example are the US plans to invade Canada. The latest publically known planning occurred in the late 1930s. Key phrase is publically known. I'd be surprised of newer plans don't exist especially since the nature of warfare has changed significantly and such planning has very limited cost involved.
There are many reasons for making plans like this. Having a war plan, even a bad one, is better than having no plan at all. It is a common exercise to train military commanders in strategic thought. Asses the strengths and weaknesses of yourself and opponent, be it in troops, equipment, position, resources etc.
I love how the author believes Cuba was independent as a puppet of USA.