Portable floodlights with generators. Myriad legitimate and other not so nice uses on the island for those.
Without any real scale it's difficult to know just how large that crack in the rocks is but at first glance it does look like a nice protected (zig-zag) passageway. I'm certain that there are other camouflaged ones for defensive purposes.
The houses/buildings don't appear to have any 'unsightly' air-con units attached to them and so I expect (but don't know) that those units are meant for the nearby building. Then again one could be enough for the building and the other an air vent/intake? That would be a good trick optics wise. Need HVAC experts here for this.
A thermal map of the island would be of great help in locating any air vents wouldn't it. Particularly of the ‘tennis court’.
Great job finding those different images anon.