That is a great thing to make sure you have in your business plan, that your business will be built around those real customer wants. Do not make callous assumptions, or statements like "I know what people want", "People are going to love this", and so on.
Marketing Plan: Marketing plan lays down the strategies of marketing which can lead to the success of business. These strategies are in terms of marketing mix (product, price, place and promotion). From the market feasibility study and marketing research, potential/ present demands of customers are determined which helps in understanding the profile of customers and hence help in laying down the strategies for segmentation of the market, identification of the target market laying down strategies for target market.
The reality is no matter how much you work with things in your head, no matter how confident you may be and how much you think you already have a great vision for your business, there are so many great reasons why you should get it down on paper.
You can concentrate so much on essential financials and supply logistics, but overlook other issues like marketing or opening times. By showing the plan to someone you trust, they can have a look and see what might be missing or worth developing more. Getting that valuable second opinion on how robust your idea is will put you in a much better position to start and keep going successfully.