If you can find a test customer to work with you during your development, that will put you in a much better place. B2B customers are sometimes open to this type of arrangement if it is a non-critical function of their business. If you strike the right balance between learning from them and tailoring the product to them, you should get value out of the partnership. When your talking to them you should always be able to effectively communicate how your product helps them save money and/or time.