Yeah, we got Sota-Nul as a stand-in new addition by French instead of getting Kelbor Hal actually involved in ongoing events as a character. Heck, she's basically leading the DarkMech during the Siege, while Kelbor Hal might as well not exist.
Mars is such a huge white spot on the map, it's just silly. We never really went back after Mechanicum, outside of the Sanders novella and shorts. It doesn't help that Cybernetica in particular was just complete videogamey tosh that wasn't really about Mars in the first place.
The Red Planet is right next to Terra in the Sol System. We've seen the Sol System and its space-geography in numerous stories. But Mars? Mars has always remained isolated and unspoken of, despite being the operational headquarters of the Dark Mechanicum, which is apparently able to have high-ranking operators flying in and out at leisure anyway.
This upsets me almost as much as it does the Mechanicum-in-exile on Terra. It's like BL cared even less about Mars than Dorn did.... and Dorn had proper reasons for not leading a reconquest force over there while prepping for the inevitable Siege. BL didn't.