Bizarrely enough, I was actually being serious.
A piezo (as I understand it, within the limits of my very limited knowledge, alternative facts are available) generates so little power compared to a magnetic pickup that it requires power to operate at all.
Some piezo rigs get their power from the instrument cable, but your bass has a battery which implies otherwise.
If you have a piezo pickup and an on-board battery, it would be odd to not have a preamp on-board too, also requiring power.
So your signal path is presumably battery --> piezo --> preamp --> amplifier and suddenly you have pretty coloured wires everywhere and blobs of solder where perhaps they shouldn't be.