Could someone check this diagram please?

[Simon Barden]

Hi and welcome.

The switch shown in that diagram won't do what you want it to. It's a standard 3-way switch, which is two normally closed SPST switches combined into one unit, which basically gives you two input terminals and one output terminal. You'll need something with three input terminals and the ability to do what you want in the way of output selection Not sure where you'll get one like that, though Switchcraft do some strange combinations for their toggle switches, but then you'll have to find one.

You've only got one output shown for each of the DPDT selector switches. so that won't work as you'll need two. The green wire isn't automatically connected to ground.

You'll also need to confirm what sort version of on/on/on switch you are getting, as in the mid position, there's a choice of two connection options depending on the switch - 1) L centre to L upper and R centre to R lower or 2) L centre to L lower and R centre to R upper.
You're missing a signal connection shown to the tone part of the pot and if that's drawn shown looking from the rear of the guitar (so you are seeing the back of the pot as if installed in the control cavity) then the two volume pot end tab connections are all swapped over (unless you are a lefty and using reverse log pots).

If you want to be able to turn one of the pickups off in the 'all on' position (assuming we can find a suitable switch), then you'll need to ditch the treble bleeds, as the treble on the pot that's turned off be will be fully in circuit and most of the treble and mids will pass through it to ground, leaving you with just the bass part of the signal. I assume this is your intent (allowing a mid+neck and neck+bridge combo) as you've shown the volume pots with the input and output lugs swapped over from the normal way of doing things I'd take the tone pot input from the pot output. Hopefully Weirdy will be along fairly shortly and he'll at least be able to give you a wiring diagram for the pot, switch and pickups.

The Switchcraft site seems to be down at the moment, so I'll have a look tomorrow and see if I can find an appropriate switch. I think it's the one Gibson use for their 3-pickup SGs, but they do several along those lines.