So, the major change in the current design is the keyboard. My aim was to make something that would look not too ugly, last long, could be made relatively cheaply and would be reproducible. I guess PCB silkscreen is the only option that satisfies all that.

My original idea was to make the button of two layers of PCB of different thicknesses, thicker top part (say, 1.6 mm) and thinner bottom (0.8 mm), such that the button would stick over the thin front panel (0.8 mm). I thought it would be a good idea to have the button pivoted to limit its free movement, and for that I planned to use a couple of standard through-hole header pins on the main PCB and matching holes in the bottom button PCB.

The plastic part of the pins exactly matches the height of the tactile switches that I used (2.5 mm). Skipping forward, it appeared that the keyboard works better without the pins, but possibly my mistake was that I left too tight a gap between the front panel and the top PCB of the keys (around 0.2mm).

The top and bottom PCBs for each key can, of course, be glued together, but a more reliable connection is done by soldering one to another (we have PCBs after all!). For that purpose I left copper pads on the reverse side of the top PCB and tented vias in the bottom part.

I don't think any PCB house would be happy to work with 10x6 mm PCBs, so one has to panelise both key parts. Here's the panelised top PCB:

and its reverse side with copper pads: 

and the bottom PCB with tented vias for soldering both parts together and simple holes for "pin suspension": 

I made the PCBs such that they could be soldered precisely before cutting it into pieces, after connecting them with four screws.

However, later I found out that it's in fact much more convenient to cut the board first, and solder the buttons later: cutting the top part of the keys is quite tedious with Dremel since they have a smaller outline than the bottom. One can still solder the cut parts pretty precisely with a simple jig to position them.

Buttons after soldering and cutting: 

(the buttons made in the opposite order, cut and then soldered, look much better).

This is the closeup how the buttons look like inserted into the front panel: 

As I said, finally I've decided that the pins are not needed, so the through holes in the main PCB are left unoccupied: 

That's it for the keyboard part. The rest is coming soon...