Sikozu was not originally meant to be the spy. It was going to be Noranti, but the actress was having issues with the makeup, so they reduced her role in PKW. If you look, there are actually two different actresses playing Noranti throughout the movie.
I don't know that it's confirmed
that Noranti was originally the spy, rather than simply suspected
, based on what is
confirmed - that Noranti was originally going to have a bigger role until she had problems with the makeup. (She really was Zhaan 2.0.) Unless there's something I missed.
We don't know who originally hid the Eidolons. All Vala says is that they were "enemies of peace." Sounds Scarren enough to me.
I believe this is very likely the case.
Look at how the Eidolons set up their servant races. They created the Sebaceans to be their foot soldiers, and the Interons to be their scientists. Then look at the Scarrens. They recruited the Charrids to be their foot soldiers, and conquered the Kalish to be their scientists.
Almost as if they were trying to emulate them in some way. Sounds to me like the war was originally between the Eidolons and the Scarrens, and after the Scarrens won at Arnessk, removing most of the Eidolons from the picture, the Sebaceans took over the war.
Or here's a wacky idea that occurs to me just now. People go on about how the Scarrens kinda look like dinosaurs. What if they are
dinosaurs? What if the Eidolons went and picked up some fearsome creatures to be their warriors even longer ago, but lost control of them and somehow created the Scarrens, who evolved over the millennia into the forms we see now? And in an attempt to correct their mistake, the Eidolons went back to the same primitive planet and picked up the latest dominant lifeform there for their next go round? Actually never thought of that before.