GK-KIT-BG3 Bass : Tricky, but worth the effort.

If you are considering installing this instead of the external one, bear in mind:

As a bass player, you still need to change strings for loose vibration to track better but just enough it doesn't catch any fret buzz, clicks and clacks.

I settled on the DIY pickup kit because it was the cheaper option. Took me a while to measure, drill holes, hide it to an active bass and get this signal sent to Roland GR55 successfully.

It gives you loads of options and sustainability over the external pickup since it's a split signal and doesn't affect your clean tone since you are going to use an extra proprietary cable. It's not a regular 5-pin MIDI OUT, but a 13-pin that only goes to Roland devices. However, you can pretty much send it literally any synthesizer in the chain with MIDI IN.

Your guitar cavity needs to have enough free space for a Raspberry Pi sized circuit board.

No need to learn japanese to understand manual, just use the circuit diagram.

Manual has both active and passive bass diagram. I might even try to put one on a passive bass in future.