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. Have you done your research? Do you really know that the people you will be targeting want your product / service, and crucially do they want it AT THE PRICE that you will be offering it at? Whilst confidence in your plan is fantastic, you must make sure that it does not lead you down a blind alley along a path that is not desired by your target market. Don't assume what customers want, do your research and make sure that is clear from the start in your business plan.
So, although a detailed business plan may not be required for an online business, I am going to include it here so you can at least look at and consider each section and determine yourself if it applies to your business.