I have a concept now.
Quarian Engineer, a Machinist that actually studied medicine and biology. Also, she's just a little . . . out there. She's still on her pilgrimage, because she knows EXACTLY what she wants to bring back, but hasn't succeeded yet. She's currently involved in junk-diving, black market shenanigans, piracy, and pretty much anything she can do across the galaxy to get the funding and supplies necessary to try and make medical nanomachines to replace/supplement the weakened immune system. At the moment she's gotten the nanomachine's efficiency up to about 72 minutes, before they break down (So at about the hour mark she freaks out and runs to scrub down and get her enviro-suit back on!).
Also, making the successive version of the nanomachines is INCREDIBLY expensive and difficult, so it takes . . . effort. On the plus side, every now and then she can feel the sun on her skin, or touch other people! Note, I'm still looking for an image to use for the Quarian race out-of-suit that's nice enough. Any help on that is appreciated.
(Speaking from a combat perspective, her specialities are slapping Medi-gel on people, emergency hacking, and using a combat drone.)