I agree that sounds like a reasonable approach - but in my working life it's always been seen as this fantastic wheeze of 'let's charge one customer to build something and then go off and sell it to everyone else!'. It seems like a great idea, but the usual story is that either making it generic burns up days that would otherwise be spent meeting the specific customer's requirements, thereby ensuring a worse product, or you stay on track with the customer's requirements and ditch the idea of making it generic as soon as days get tight.

This is one of the things that always makes me groan, along with 'and you can learn x technology along the way!' >:|