First hypothesis (hopefully I'm over-thinking this): Yes there will be interplay between the "modes" and therefore I need to cut off the interplay-connection to the mode that's not supposed to be active.
Potential Solution?: Swap out the push/pul for a 4PDT switch where the 4 poles perform:
1- Selecting whether the neck pickup goes to the blend or the 3-way switch
2- Selecting whether the bridge pickup goes to the blend or the 3-way switch
3- Connects/disconnects the wire from the blend pot to the volume pot
4- Disconnect/connects the wire from the 3-way switch to the volume pot
Someone please tell me this is over-thinking as I'd much prefer to push-pull...