I recently purchased a 5513 replacement case from Vietnam (MQ) and I can say that it's a very good deal in my opinion. I only purchased the midcase since it was all I needed so the price was good considering you have no choice now. (Cartel cases are no longer spec. for fitting crystals).
The best part of paying for a 5513 replacement case from MQ or other high end case makers, is that you can either use an ETA adapter ring from Yuki or put a real 1520 rolex movement in them when you get the funds.
I got tired of fighting with the Cartel case and just paid for an MQ 5513 case and I love it so far. The quality is amazing. They even put the small cut out where the rolex movement screws slide in. It's just like the real case as far as I can tell.
I doubt it but maybe it's possible. Normally, 3D printed items that end up in metal are first material jet printed in castable resin or castable wax, and then the model is cast in the final metal. However, there are one or two types of printers that create stainless steel directly. But...... as far as I know...... Material Jetting type 3D printers have the absolute best resolution. I make my jewelry designs using services that print my models with material jetting machines and they they cast it for me or they send me the model and I cast it in my garage.