O.K. I used to own a Hofner violin bass back in the 70's.
I don't remember touching the controls other than volume.

Looks like all the controls do the same thing...either turning one or both pickups off or turning either down.
Therefore you could wire up a control plate with just 2 pots and one 'mustang' 3 way switch.

Click image for larger version. 

Name:	Hofner switch plate.jpg 
Views:	234 
Size:	69.3 KB 
ID:	37643

cheers Mark