I love the promise being offered by 3D printing. I've long been after different loco bodies for existing N gauge chassis, but right now I'm into the last stages of painting and detailing a 3D printed ex-LSWR royal saloon in N, and I have to say it's looking pretty marvellous. It'll certainly never be available through any manufacturer as it was withdrawn in the early 1930s, so 3D was the only way to go.
Before you know it there will be quite a crowd in this thread offering you hints and tips. I'm following around half a dozen similar threads right now, and everyone seems keen on making it work.