I got it!

Spoiler: pics
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What did I do? Well, I don't know exactly, because I've been changing things here and there. First I injected the "buildings.ini" in the Pongo skin zip wherever it occurred to me. I also changed things in the defaut.vis of the Data.zip, but it still didn't work.
The key was to change the luna_sign.zip of the Pongo ux for another, I think one of the Aldo skin and then ... The buildings rose from the ground !!