After a lot of hesitation I finally made an attempt to put the thing together. It went on with variable success.

For the future reference: the gray top is MJF Nylon / Natural Gray / No surface finish. The white bottom is SLA / CBY Resin / Faint yellow / General sanding. 

I made a lot of mistakes in measurements, so the display can't not fit in the window I left for it. Oh well. This offsets everything deeper, and of course it makes it impossible to close the back lid. With some cutting and swearing I was able to close it. The back lid cracked in several places, but it's the least of its problems.

Unfortunately, for some reason the SD card errors are making a comeback. Power issues are all back too so they're probably related. It's as if something happened to this board while it was waiting to be put in the case.

I think I should reconsider powering the keyboard pipico from the onboard 3V3 and power it with VBUS instead. I suspect ESP32's own regulator on this board is underpowered. As for the case, I think it calls for a second iteration, even though I'm not feeling very enthused about it at the moment.