Kilemall, lots of variables here, but I will give some comments that may help. Based on military and civilian experience both with medical training, as well as watching others work.Hmm I should clarify what I mean by combat medic. I’m thinking in terms of units like special forces. I understand they all get at least minimal emergency training but the dedicated specialists.
I have DMs for field equipment vs medbay/ambulance vs hospital/surgical unit and TL in addition to TL. Typically resuscitation/stabilize to avoid shock roll first, transport roll, then we get to recovery or surgery.
"1" being the Traveller default for "can get a job doing this" would then equal (in U.S. parlance) a typical EMT/military medic. Capable of doing more than just basic first aid, administer some simple meds etc, but not great at long-term care & such (again, being VERY general). OR, this could also represent your nursing assistant/LPN levels - again, basic daily care and such, but not going to be diagnosing things or prescribing meds.
"2" you're looking at your "Paramedic" level, or your mid-range Special Operations/Independent Duty medic. Administers more meds, does actual medical interventions, starts some basic diagnostic stuff. Given the 2D6 range and how bonuses quickly impact things, I'd also allow minor surgery and such, particularly with high-tech assistance - so, stuff like suturing, extremity wounds and so forth. Nothing inside the thoracic cavity (except for needle decompression on a pneumothorax, but that's getting WAY more detailed than I like my games). OR, looking at RN/possibly Physician's Assistant - focused on the medical/preventative care of things more than trauma and emergencies.
"3" in CT is a Doctor. If your game was structured as such, yes I would also include your higher-end Special Operations medics, particularly with some of the training advances of the past twenty years - could only extrapolate such being possible in the future as well. So, covers not just basic but advanced trauma care, community medical care, preventive medicine, and so forth. If you aren't including PA's at 2, then definitely at 3.
4+ you start getting to the specialty care, being an educator as well as a doctor, and so forth.
Another important note (and, a quick way to see people start a debate) is remembering that "pre-hospital emergency care" and "hospital/doctor's office care" are two completely different worlds. There are some fantastic, experienced, skilled paramedics who would have no clue how to handle an oncology patient, despite this skill. Similarly, there are nurses who are amazing in the hospital setting who wouldn't last five minutes trying to stick an IV, while reading EKG leads, and dealing with a moving vehicle as it bounces across potholes. Each side has a use, and one isn't "better" than the other, despite what egos start to say.
If I was running a game? "Well, what's your player's background?" A Medic-2 attached to the Scout Service for her whole career can pull off some different tricks than that Medic-2 who came from a noble background, high-tech, high-pop world.