As an example, let's say your current average number of transactions per month per customer is 3ǌ. Which says on average each customer does business with you 3 times each month. You could calculate how much more profit you would get if you could increase it to 3Ǒ. And I can tell you that would probably be enough to meet your plan. And if that did generate enough profit, all you would have to do is maintain everything else; sales, expenses, labor, average dollar sale, etc, and then just figure out how you could increase your transactions from 3ǌ to 3Ǒ. Maybe it could be with some type of promotion that would get customers to come in more often.
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.