OK, here's a challenge for you that combines 3D printer and Tron.
Both
Paradise Arcade and
Ultimarc carry a triggerstick like this.

The original
Tron Joystick uses a special
restrictor plate that makes it more difficult to hit diagonals unless you press the stick a bit harder.
It acts as a 4-way restrictor for light cycle and battle tank levels -- light pressure on stick misses diagonals.
It acts as an 8-way restrictor during the I/O Tower and MCP cone levels -- slightly heavier pressure allows you to hit diagonals.
Can you develop a printable Tron restrictor that sandwiches between the microswitches and the bottom plate on the triggerstick?
Alternate approach, CNC or laser cut one from 1/8" neoprene similar to
this.
Before anyone brings it up, I already know that automated 4/8-way
in-game switching is possible, but this restrictor is for someone who doesn't have the software skills or auto-switching sticks.
Scott