Thanks for your help

but i talked to some experienced bassplayers and they told me some possibilities how it makes sense to change the electonic. How to make it more really usable. In most cases like to keep things simple and even usable. So after i thougt in-depth about the way to change it i made the decision that i will completely change the electronic as they told me to to it:
- 1 volume knob (for both pus)
- 1 treble knob (for both pus)
- and the 8-way switch leaves for an 3-way switch (front/back/both pus)
If someone is interessted i can upload the pictures i made of the original electronic.