A business plan is simply a plan of what your goals are for the business, and how you plan to go about accomplishing them. Some people refer to it as a vision for your business. I like to refer to it as a blue print or a road map to accomplishing your goals. Your plan should be spelled out in clear and defining terms and be kept simple. It should be a written document and used as a tool in managing the business.
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.