What ab
What about using a double pot and stacking the bass and treble, another double pot for the mid (with or without a mid sweep) and then, the last hole is already drilled for the pickup coil splitter?
Otherwise, why not try the 3 positions of the mid sweep first (to see if you really need all those options) and then leave it set to your preferred frequency in the control cavity?
IMHO the basses I have had with this type of mid adjustable circuit have not proved very useful in practise. Mids sound wierdly unnatural to me when boosted and when cut, you can disappear in the mix. However, I also found I only ever end up lightly boosting the bass frequencies and cutting the active treble on an active bass and prefer doing that now directly on my amp. Then it's just a question of using my passive tone control on my actual bass to remove finger squeak or metallic overtones -eliminating the possibility for over-option anxiety and battery hassles. IMHO, etc. etc.