Why needs 3-rail switches polarising?
At short switches (Bild 1)
you don't need polarising absolutly
Other than using long switches (Bild 2)
As less the angle of branch line/crossing line, as longer the distance between the pukos.
If the distance between the pukos more as half length of pickup shoe,
he touch the rail. (Bild 3)
The best answer to evade a dead short is polarising.
For polarising you can take two changeover switch.
Usually integrated there are in switchmotors (for exemple Servo MBTronik WA5)
example of circuit: