Not everyone is able to figure these things out right off the bat.
We were referring ONLY to my clearly surreal "reinstall windows after reinstalling" sentence, that could only be a typo.
In any case, what we found in the Teamviewer session, it's clearly a newly discovered P3D bug: it seems that a corrupted EXE.XML in the %PROGRAMDATA% folder, will prevent *all* the other .EXE from loading, even those referenced in their own add-on.xml. What makes the bug more interesting, is that a corrupted EXE.XML in the %APPDATA% folder, instead, DOES NOT cause any troubles, and it will be just ignored, as it always was the case.
In our case, the corrupted EXE.XML was caused by the section related to the UT Traffic Live misplaced and outside the <Simbase.Document> tag (it should be inside), making it an illegal XML.
And usual, what it might have been easy to assume as a "Couatl doesn't load" issue, didn't had anything to do with it, and neither Couatl was the only .exe affected, since the AS16 .exe didn't start too, and of course the UT Live didn't, which was what seems to have caused the problem in the first place.
Of course, I already reported the issue to LM, in their developers forum.