Bsee, I am with you on few things. I did not understand at first what you said about the MXY.
I understand what you're saying about PU placement and more/less variations, I though about it, but the thing is I do slap as well, and the PU too close to the neck is not great for that (me at least).
Further, you answered something that relates EXACTLY to my post, SPOT ON! you say: Looking at your proposed setup, the spacing is going to be awfully close between the pickups such that you won't get as much variation to play with. This is exactly why I wanted the third filter + Q-switch! So, I am aware of this, and for now, the good option is the PU/Filter selector trick that I described above.
Regarding placement, again, I am with you, I would prefer the Filters closer to the PUs, but I am trying to keep things tidy and minimize cable extension, because the Q-switches would be further away from the Filters and would require some extra work. Anyway, you are right, I am going to get this positioned properly, after all, once it is in the cavity, who cares what it looks like!?
So the volumes will becomes the Filters and vice versa.
Thanks for pointing this, this is very important. I did think of it, but now I am going to get it done properly for sure. Luckily, the Luthier hasn't stared the wiring yet. Now, I have to decide where to fit the Filter selector.
Somatic, thanks for the link.