I was actually so excited about the idea with laser-cut button caps, that I scrapped the design for version 5 that I had lying around, waiting for the new buttons to arrive to make sure I have the right footprints, and made a version 6, going back to the standard tact switch buttons, with an SMD piezo:

I also moved the holes a tiny bit away from the edges, to make the acrylic a bit stronger, and added a hole in between the d-pad buttons, so that I can experiment with placing a plastic bead in there, so that the d-pad cross can tilt on it. We will see how that works.

The top plate of the case now has cutouts for the button caps and the caps themselves:

I also included a second version of those caps, with a cut across the hole to increase springiness, in the middle plate design. We will see which one works better. I will probably need to tweak the hole sizes a little bit anyways.

There is also rubberized sticker paper that I can put on top of the caps, to cover the holes and make the surface better for the grip. I will be experimenting with that later on — I'm still toying with the idea of having a sticker in between the layers, then the cap covers could come from that too. Seems like you can get custom 10x10cm die-cut stickers easily.