This is all speculation, but I think they were gonna make Sylux into a male version of Samus. Someone (potentially even a relative or friend) who was on K2L with Samus as a kid and didn't get rescued by the Chozo, but instead got captured by the space pirates. A "bad egg" version of Samus to continue the bird references. This might have piggybacked on the original Metroid Dread project (the one teased in Prime 3) but then the name and hype of that game was co-opted by Sakamoto and Company. Instead of being infused with Chozo DNA and being made the scion of their lineage like Samus was, Sylux might have been experimented on by the space pirates and turned into a human weapon, one capable of interfacing with human systems and stealing GFed tech covertly. But Dread had ganked the "familial relation gone evil" plot by 2021 - so Sylux's original backstory might have been thrown out...