I should have been a bit more specific. their idea is the ability to walk in of the street and have your idea made. that is not much different than what you are suggesting. Your idea is sound as long as it fits with what the market wants? these days they all want it yesterday and exactly how their mind sees it. Have a look at their business model not necessarily their business. You can go almost anywhere and get what you want these days, it all boils down to cost and speed to supply. Personally i think you have a sound idea just do a bit of homework with some PR. Are there local business that could use your service? go ask first and gauge the response.

Good luck