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.
A business plan contains several main elements. First, it lays out the mission and the goal of the business. The plan will spell out whether your company is in business to serve a greater good or simply to fulfill an unmet need. Determine whether your business will serve other businesses or supply products to consumers. These are all important elements that should be included.