What makes an old Nokia indestructible?
- Low mass
- Flexible materials (aka no aluminum plates)
- Simple design
- Easy to (dis)assemble
So my guess would be a 60% board (low mass) with PCB-mounted switches (much sturdier) and either a polycarbonate or carbon fibre plate (again, low mass/high flex).
Think along the lines of the
Smallfry Kit or the
CF60 Ultra-light Carbon Fiber 60% Case but then with a CF plate on both sides.
Also, no LEDs, as extra solder points mean more points of failure.
Put in a high-quality double sided PCB and you are golden. Your most sensitive part would be the PCB if it cannot stand the flex.
Bonus points for
SIP socket mounted switches.

It will completely explode when dropped but can be put together without issue time and time again.
That is assuming of course, that you care about dropping your board.
For general daily use on the go I would give my vote for the Leopold FC660 models or the
police Déck/TG3 boards.
