Hello, Mica!! Hope you had a great weekend!
First of all, idea; Do you, or have you, ever used stacked pots? I don't recall seeing any in the archives, but if that's an option, a stacked Bass/Treble set would be fine, and we could keep the Master Volume with a minimum of hassle. Just a thought. I would really like to keep all the controls if we can.
If that idea is not possible, choice #2. From my research and some very helpful input from other Alembic owners, most notably Mark Shepherd, here is what may be an option to work in all the controls in an a attractive and functional manner:
Mark's 8 string has the same number of knobs, and more switches, so I think this will work! I really like the design you came up with, and this keeps the basic configuration while working in the additional Master Volume control and toggle.
Looking at your layout, 1) begin by spreading the knobs on the upper and lower row as far out and close to the cavity edge as possible.
2)Add the Master volume where the Neck volume currently lives.
3) Move the neck volume where the 4-way is now, leaving the Bridge volume as is, just closer to the bridge as earlier stated (you'll see...)That keeps the volume controls all in line and order.
4) Move to 4-way to where the Q's are on the bottom row.
5) Next, adjust the output up just a hair, to make it symmetrical with the rest of the middle row, while placing it as close as possible to the cavity edge towards the bridge end.
6) since the toggles are more space efficient, this should work-Place the Stereo/mono switch logically next to the output.
7)Bridge Q toggle next, bridge filter knob follows.

Neck filter knob, with neck q toggle to the left. Move the 2 filter nobs minutely closer together if necessary, but of course as far apart as possible.
9) LED toggle last in line, closest to the cavity edge towards the neck.
10) Bottom row- Bass control, 4-way p/u selector switch, treble control, all spread out symmetrically to mirror the top row.
Mica, you are the expert and know how much can be done, the final call is up to you as to whether this will work or not, but it appears to me to be logical, attractive and functional. What do you think?? Workable?
If not, do you have any other idea's on how we could work this up? I would rather exhaust all options and explore all scenarios before we start deleting things. I hope I'm not being too much of a pain, as it is not my intention. I would just like to have my ultimate Bass! But, I'd also like my own Island in the Caribbean =)
One more minor detail- with the single set of Bass/Treble controls on Anniversary Electronics I believe in Stereo mode they will only work on 1 pickup? If that is the case, which pickup would not have the control? I can deal with that, as I'll probably only run mono for now live, probably using stereo mostly while recording. Just wanna know.
Welllll, just check this all over an let me know whatcha think. I definately don't wanna rout out anything else. I kinda want my bass!!!!!!
Have a great day, and have fun!! TTY, Mike=]