Something like what you are describing would be insanely expensive to achieve. My time is definitely not free, even if it's a project for myself, I still consider it. I don't see any way to make this an actual business, let alone profit from it. Unless you are going to do it all for free, then by all means be my guest! The amount of time required, would immediately set it as unrealistic. For instance, if a consumer is fixing/upgrading some appliance/furniture/toy in their house (like you are "fixing" your 3D printer), you would have to receive the actual part in question (possibly what it is installed on as well) to reverse engineer the part then make the necessary changes. Or you could take some wild-ass guesses and do the whole Trial and Error thing. This already makes it too expensive. Shipping can be very expensive especially if you are not receiving discounted rates from your carrier of choice. Even if you leave the shipping out and have a local 3D printer print it and the consumer picks it up, still additional costs involved. Unless you have the consumer try to explain what they are looking for, but then you are creating a ton of complications for yourself. Plus if/when you get the part wrong by not having a hole in the right place it will always be your fault, even if they told you that is where it needed to be. And you will have to eat those costs. Honestly, a 15 minute conversation on the phone with any designing/engineering company, would likely set the consumer above their budget for the part in question. Most consumers have no idea the concepts of modeling, which makes communication very difficult. Or the ongoing costs that go along with the profession. I work with SolidWorks everyday and when I am working on a specific project my time is $100/hr. During the initial meeting, most people either have no idea what they want (they will expect you to know, read their mind), or they know exactly what they want but the product can't be manufactured in that way. Which, again, creates tons of complications. Not to mention all the headaches. So all in all, way too expensive even for someone who wants to throw a lot of money away. Plus with all the websites that are currently doing similar things, it would be hard to get your feet wet. Also if the consumers have so much money why not just buy something they actually want, instead of wasting time with this process. In your instance, they would just buy a new printer. I do like the concept, as I do not have a 3D printer at my house (just at work). I wish I did as I have lots of ideas. So if I wanted to have something made (for instance: the new windshield washer fluid lid on my car which I ordered from RockAuto, a low pressure A/C cap, or a new gear for the sunglasses holder) it would be convenient. Cost Effective? Absolutely not. We are a consumer country: if you don't like it, throw it away, and get one that you do like.