Thanks!
I actually came across that flicker series of pics while scouting the web desperately for more info.
From what I've read, once all unnecessary wires are gone, 4 remaining wires need to be extended in order to relocate the fuse and relay1 boxes to the old passenger airbag spot.
Good call on the immobilizer.
I started to go through the schematics in the Bentley and highlighted all the stuff I can pull out. I also found this video interesting for removing terminals from a connector:
removing terminals on the VW wiring harness - YouTube
It should be similar on the Boxster connector.