Did you ever stop and think what a unique position you're in as a business owner? I don't know of any other way you can have as much control over your success than owning a business. When you work for someone else, you are totally at their mercy as to what your future may be like. It doesn't matter whether it is a private business you work for or a large corporation. Your future is in their hands. The only thing that might qualify other than owning a business would be to inherit or win a lot of money that would give you everything you want in life. So, why make a business plan the normal way when you could first make one that could give you what you want in life? Have you ever thought about doing a plan like that? Would you know how? Would you have the time to do it?
Another consideration. Should the business plan be a document that is focused on selling an idea for a product or service? For many years I worked in a company that did not want anything in a business plan that could be construed as showing a bias towards or against a project. The mantra was to only present facts in the business plan. The Operations Research Department was there to review the analysis as being unbiased. To handle the "what if" scenarios or sensitivity analysis we prepared a supplemental analysis documents which were mostly financial oriented. Personally, I like a factual approach and use the presentation of the final document to point out the conservative aspects of the content.