As a follow-on from the diagrams, there's one other option I should mention: the Free-way 6-position toggle switch. it's an expensive switch, but may be easier to obtain than the double-neck switch.
The interesting thing is... by using this switch to do some creative switching of the pickup negatives/grounds and how they connect it should be possible to have 3 positions for the guitar pickups (bridge/both/neck) and 3 positions for the bass pickups and you won't need a second switch at all (although there wouldn't be a 'mute' position). So, you could plug the upper switch hole if you're going for a solid colour. Anyway, just another option.