I have written business plans for all manner of industries: a coin operated jukebox company, airlines, travel companies, new product launches, and anti_aging product companies. It is not necessary to have a passion for the product or the company to write or develop a business plan. What you must have is a passion for aggregating information, getting involved with and understanding the service or product, and understanding the financials of the product or service. By financials I am not referring to having a CPA before you undertake the task, but rather understanding the presentation of the information and analysis/ numbers to support the activity being planned. Financials are important because they are the score card in the world of commerce.
It may be easier than you think to figure this out. You would do some research and with the aid of the U.S. Census Bureau you can roughly determine whether your plan can be supported by your market or not. So what do you think? Is it better to build a business plan around what you want in life then see how your business can maybe give you that or is it better to use a sample business plan for a small business where you are probably guessing?