So my plan is to make a full size case that will be as authentic looking as possible, with beautiful walnut sides for sure. I may 3D print the blue panels instead of using sheet metal so the build would be accessible to more people should they decide to make one.  

For the keyboard I have been in touch with Dave from osiweb.org who has designed a complete replacement keyboard for the Sol-20 using modern Cherry key switches. From the Unified Retro Keyboard Project:

The keyboard is not a replica of the original. It doesn't use the same capacitive circuit or keys. But it does have exactly the same layout with the same functionality, including the 3 LEDs (UPPER CASE, SHIFT LOCK, LOCAL) and 3 outputs (RESET, BREAK, LOCAL). It uses cherry MX or Futaba MD-4PCs keys. Neither has quite the same feel as the capacitive keys, but the Futaba keys approach the travel of the keytronic switches, and do have a nice feel.

I'm getting the keyboard as a kit and looking forward to putting it together.

On the inside I'm going to emulate the Sol-20 hardware on a Raspberry Pi 4. To that end I have a working (very basic at this point) Python based emulator I'm going to post to GitHub shortly. 

I haven't decided what to do for a monitor yet. Certainly a CRT of some sort would be ideal, but I may have to go with a LCD.