This is the end result. It still misses a decent cable sleeve and possibly better screws, but it's 100% functional (I'm writing on it right now).
As I said this is my first experiment and it has been an entertaining project. Before this I had no idea how to build a keyboard from scratch and I have very little electronics skill, so if I can do it I encourage everyone to try.
The case is 100% stainless steel. I wouldn't recommend using SS actually. It's a hell to work with. If I had to start over I'd probably go aluminum or even acrylic.
The good about SS is that the keyboard is rock solid, there's no vibration or rattling parts. It's so firm that makes a Filco feel cheap. All you hear is the sound of the switches. Very pleasing to listen.
The bad is that it's really too solid

I was not able to find someone who could help me design a PCB so I ended up with wires

Being the case all metal I had some problems with shorts, but I've been able to sort them out. Soldering took me almost two days. The firmware is a modified version of the GH60.
What next? The idea was to make a group buy. I don't know if there's enough interest in such a thing. I'm definitely going to build a second keyboard, this time with ALPS and a more standard layout, basically a 60% + arrows similar to the Leopold 660m/c
I'd like to try a mixed aluminum/acrylic case next time, though.
If you have any question regarding the making of the keyboard, don't hesitate to ask.