If I'm successful! Will do my best to document this mod and will be happy to share the results good or bad. Gonna dummy it up and test it before I drill any holes.
You're not gonna get the unplugged sound by bypassing half of your
current tone chain, which is an integrated system, and not designed
deliver the voice of the PU. It's built to deliver the electric bass voice
of the complete package.
Go try a piezo Sterling and crank the pan to 100% piezo. Now THAZ
the loud version of the unplugged sound Weeelll ..... sorta, kinda.
Aftroll you'd still have the pre-amp engaged with it's contour thaz on
duty even if you think you've set the EQ to flat .... cuz it's contoured
to compliment the nature of the ceramic magnet PUs.
If you really wanna play the loudified version of the unplugged sound
you CAN do it without hacking up your ax. You'd need a piezo under
the bridge, fed via a switched lead to your output jack or volume pot.
Raw piezo output needs at least 1 megohm input impedence. If your
amp doesn't offer this, you'd also need an "acoustic preamp", such as
a compact Fishman or Baggs, between your ax and your amp. This is
all quite do-able and nothing exotic. Contact [Bob] Golihur Music, or
Dave Wendler, or your fave URB shop.
I agree that you won't get the unplugged sound when bypassing the preamp. Further I don't see any sense in doing that modification. Those basses are perfect as they are.
If he's fine with voiding his warranty, I don't see how this mod is any different than the passive option on the Classic models, or the Reflex, Big Al or gilded white special edition (minus the passive tone control).
That said, I don't think it will achieve the stated goal.
Just a quick update, I'm running through the 5 way switch then out to a 1 meg pot then the jack. I totally love the sound I'm getting! I will put the appropriate switch in when it gets here and hopefully get y'all some pics.