Think about each aspect of what you write down in practical terms, picture it happening, how will you get hold of the assets and equipment you need to make your dream come alive? If new buildings are going to be built, is that realistic, or just a dream? The temptation is to get carried away. By all means dream, write down big aspirations. But then make sure your intentions are to actually do what you say. That is why writing a marketing plan isn't a one man job, because the goals and dreams written down aren't going to be achieved by one man. You have to know that the people essential in achieving these goals are ready to tighten their belts and commit to getting there. One man can't tell an organization of people what they are going to do for the next five years if they have absolutely no aspirations of wanting to get there.
Writing a marketing plan without any buy-in is like driving past a beggar on the side of the road, giving him a peace of paper asking him to write down your life aspirations, before driving off. I can guarantee that his list and your path will never meet. He'll say you became an artist that retired on some tropical island in a hut, you'll become an accountant in the city, your not a creative person. This brings up the most important reason why this approach is flawed, his aspiration list will not be based on any knowledge of you, but rather on random thoughts, and so it is with a marketing plan. Your plan will say that new buildings must be built to cater for the new aggressive marketing of 5 million consumers, behind the scenes, the accountants will be preparing for a financial crisis.