What confuses me about Sylux is the rationale for his inclusion.
It's not because of his move potential, or the fact he's an interesting character, or that he has a cool design. It comes down to "Metroid needs more reps". I agree, but just because Metroid should get another character doesn't mean we should settle.
Aside from Dark Samus, you have other hunters who are more interesting (although I personally don't think any are worth advocating for). Weavel, for example, could be interesting, given his ability to divide into two parts. Sylux has... the shock coil?
Maybe there's a rad moveset out there, but I'm curious if anyone has a reason more than "Metroid needs more reps".