I would personally suggest adding a Tone TwEQ for a completely adjustable 3 Band EQ which both adds tone as well as cut tone (in a shelving manner). This to me would be very much like a mini Bass preamp as long as it is built to Bass OD specs and the Tone TwEQ is already Bass Ready (which is why we have two separate boards so folks will actually try one or the other based on their needs). We have no plans for any type of parametric EQ as there is just not enough of a need for one currently.
I would suggest wiring it like this so you only need “One Volume Pot”.
The Tone TwEQ Volume Pot is replacing the “Main Board” Volume Pot in this example.