Master volume is critical to me. Every bass I've had with two volume controls is a PIA on stage. Probably from years of playing Precisions and StingRays, but I just want one volume control. A decent blend pot PROPERLY wired works well with both passive and active P/J basses in my experience. Make sure it's a blend pot, and that you have the hots of the blend and the ground connected to the correct part of each pot gang's resistance path, and that the PUPs are in phase. It'll be electronically just like a typical Jazz bass-style V/V/T, with the addition of an extra volume pot (the master) in the circuit. And that's a pretty minimal tone loss in the real world (assuming good PUPs, cables, and amps).
jte