Look at the assumptions you baked into your original plan. Did the city follow through on opening that new park across from your location? Were insurance rates what you expected? How many hours of accounting or web design help did you really need? Are your online inquiries out_stripping your face_to_face sales? Or vice versa? Sometimes no matter how much you research, plan, or test, things don't go as expected in a business. This isn't necessarily a herald of failure or a sign that you're not cut out for entrepreneurship. Life and the marketplace are both unpredictable, and plans need to be fluid and responsive. The "One Pressing Issue Plan" is simply a reflection of a normal evaluation process.
If a document needs to be developed that requires input from other disciplines_Finance, HR, Property & Facilities, Marketing, Procurement/Supply Chain_ then most likely you are looking at a team building effort to get the job done. In any event, don't look at the task as only as a roadmap that leads to a profitable product or enterprise. Business plans are a great way to build team buy_in, force a thorough review of options, define objectives, establish benchmarks to judge performance, and help arrive at a plan_of_action. Ultimately, it can lead to a Project Management approach to implementing a plan and that can be as involved and detailed as is necessary.