So, I was about to wrap this project up after looking into a few anomalies, like the non functional spoiler. I had a look under the rear of the trunk liner and found this:
All those connectors don't do anything, they start and end on the same wire. I assume something else was connected at some point. Also the red wire has been added, it goes from one taillight to the other...???
and this:
Those holes are supposed to have the bolts holding the spoiler motor in them.
plus this:
Looks like the connectors for the spoiler motor and the trunk lid opener.
It seems this car has some more surprises and tasks for me!