This bass originally had Essence electronics, volume, pan, filter. What looks like is in there now is volume, bass, and treble mounted, with the pan board as a floater inside. Not very adjustable, but perfectly OK to do.
You can swap out the bass and treble module for the filter module, or you could mount the pan where the bass cut/boost is and drill a hole above the jack and undercut the cavity (of course reshielding) and mount the bass control there (I say the bass control because it's a single pot on a small board and is easier to sneak into tight spaces).