I really like this idea, but with current technology its a non-starter. 3D printing would need materials which improve in orders of magnitude upon the strength,

I really like this idea, but with current technology its a non-starter. 3D printing would need materials which improve in orders of magnitude upon the strength, the heat resistance, the hardness and the printable accuracy. Not to mention that the materials must be available in a reasonably abundant supply. I do however think there is probably scope for 3D printing small replacement parts (I'm thinking of things such as plastic pump impellers etc) , if not at home certainly at a main dealer. I doubt this would come cheap but that might be balanced against the reduced turnaround times and ability to maintain a smaller supply chain.