Finished this yesterday - it is an onboard EQ that is based on the "Variable Spectrum Control" (VSC) on Blade Guitars. Here is an image of the original (it will fit in most regular guitar cavities as well):
(http://www.bladeguitars.com/typo3temp/pics/c44b8de0b3.jpg)
You can set two presets with the trim pots and select them with a mini-toggle switch on your guitar: One Mid Boost setting and one setting where you set a bass and a treble boost. With an On-On-On Switch a third setting will be the umodified guitar-signal (true bypass). Here is my take on the circuit:
(https://s6.postimg.org/olgsqq1c1/Full_Size_Render_2.jpg)
(https://s6.postimg.org/lsnl6p0zl/Full_Size_Render_3.jpg)
(https://s6.postimg.org/pqauw3nsx/Full_Size_Render.jpg)
For a better understanding, here is the preset chart of the original:
(https://www.amazona.de/wp-content/uploads/2099/09/VSC.png)
Boards available: http://www.madbeanpedals.com/forum/index.php?topic=25099.msg244381#msg244381