This would work, only the stick's throw is so short, it hits the diagonals as easily as it does up/down/left/right. I think maybe I need to find something to act as an actuator thats diameter isn't as large as the one that comes with the stick; thus making the throw longer and making the diagonals harder to hit.
Then maybe I can make a restrictor like you're saying...
Hey I have a few 4/8 way switchable joysticks , you change then by using a smaller diamater plastic piece (actuator?) So I think you are on the right path.
Just my 2 cents
Ed