you can also tip over a cube() by 45° and difference it from your object to take off an edge.

hull() between 2 cubes would be my strategy for rhombo

https://github.com/wolfwood/navcaps

you can 3d print an adapter to place a thumbstick in an MX keyplate socket. and keycaps. 5 way switches tend to require more force than regular keyswitches, but a longer stem will offset that.

check out schiller’s fulcrum keyboard as well.