Yes, the LoZ pups are very even across the spectrum response wise - one reason the guitar versions weren't very successful, and one reason Les decided to go LoZ in the first place.
You can, however, carve out a nice midrange bump by virtue of rolling off both the treble and bass tone knobs to taste (and turn up your preamp gain to compensate). When it comes to EQ Les understood audio engineering best practice: don't add if you can take away in order to achieve the same effect. You won't get that growly bite (you would from some other Gibsons, even some shorties) - these things are about smoothness not aggression.
I strongly recommend against the ART TubeMP for bass use. I tested that out vs a few other preamps with a bud a number of years back and it was very lean and brittle sounding compared to every other one we tried. He went home with a Bellari instead. The pre on the PJB should be much better still.
