I understand money can be a huge barrier..., that's why I mentioned you should look into partnering with one of those app makers to see if you guys can collaborate without you having to research or re-inventing the wheel...
Your library of parts really should be more like youtube, rather than Netflix or itune. 3D printer community for now are mostly DIYers. They're not going to rely solely on you to feed them parts. Plus, how expensive will it be for you to keep an army of CAD designers on payroll just to create parts for your customers? Longterm perspective, having a easy to use scanning tool will be much cheaper for your company.
Anyway, my suggestion isn't meant for you to call off your product launch, but just something I thought you should add eventually. I do believe this is the main reason why 3D printing hasn't caught on.
Most people have these fancy nearly thousand dollar mini-computers in their pocket. We should put them into good use.
Good luck with your venture. I'm sure current 3D printer users would appreciate your better and cheaper printer. Hopefully someday you'll compel me to also want to buy one of your printers with a easy to use scan tool!