I replaced the passive EQ on my Daion Power XB (2 vol, 2 tone pots) to replace the 2 tone pots.
It unleashed a new set of tones and restored the treble; the old passive EQ only did a treble cut, now I have bass boost/cut and treble boost/cut. There was no need to cut the bass body or drill holes. I did fit a battery box in the rear cover plate to make things easier. Battery life with my EMG pickups and the BTS on the same 9v seems good.
Unless you replace everything you will need to do some soldering; the plug and socket wiring is fine if your existing pots / pickups have them. It's not difficult soldering though. As a bonus the new pots are considerably smaller than the old ones so it left room for the battery inside the cavity.