This is great! I just asked this question yesterday. I was asking for a Medical based X-book I had created in 2006, then commissioned in 2014. I have adapted the team and concept through the different story arcs, to include the latest Hickman run.
on the Age of X-Men Facebook page
people came up with:
Balm
Barrera
Brace
Doc (unofficial)
Force field
Safeguard
Shell
Suture
Truss
Mark Johnson: Doc. it would be an unofficial codename (like Kate Bishop in Young Avengers, when they jokingly call her "Hawkingbird" in the beginning). The Newbie in the book or the X-person who never met her would think it's an official codename. She'd clarify, "No, not a codename. I'm a doctor, They call me "Doc" it just stuck.
I do like lifeline though, maybe give that name to Wing or Angel Salvadore?