It won’t be Mark who
Saves Gemma. I think it will need to be someone unsevered, Devon or maybe Rikon or Cobel. The family room Dylan is using could be a front for this. I think anyone who is severed probably has more than one innie built as a safeguard. Right now Lumen knows iMark knows Gemma’s alive so they are prepared for shenanigans. Someone from outside needs to get in.
It’s also entirely possible what Cobel was afraid of is what Gemma is currently experiencing. They said she’s a soldier and grew up there and it’s likely— following Field’s slip up at dinner, that they’ve been playing around with severance for decades before going public. Maybe the dentist was also the priest that recruited Burt.