Sort of like support of military exercises, like?
Yes, you can get out of your depth because firefighters will conceal their degree of injury, or exaggerate it, or try self-tx that goes awry. Also, some things they do can go very sideways very fast in a major manner, necessitating fast and correct action.
Mil excercises were mostly much safer by design, but here's what I wanted my techs to learn:
1. DIAGNOSIS (or whatever you need to call it); know the criteria for calling someone "OUT" and sending them for tx. Know what you can do, what you can't, and what you should. Know what to ask and how. Know how to do basic directed ortho exam (anything more indicted need to send out for X-ray anyway).
2. GENERAL MED: people deploy while sick, or not aware they are getting sick. Foot care!!! How to apply an elastic support with COBAN. Treatment/diagnosis of minor wounds to prevent or address minor infections (anything worse after one day's treatment=OUT). Teaching about how to stay healthy as you warm them up, cool them off, get them to sit down and drink water, or just eat something. Know something about recognizing and addressing dental issues (abscesses, lost fillings or crowns, broken teeth, broken or dislocated mandible). Sick call for return checks and knowing how to get them sent back to you if needed.
3. EMERGENCY MED: know when to "pull the big red lever" and when not to. Airway, bleeding were foremost. Most true emergencies will require sending out since they are work-comp, so no splinting and sending them back to rest on their bunk, get 'em ready to go get seen.
Overarching points were know how to stay healthy/operational, know how to interface with the bosses and the troops, and know exactly how to balance operationality and duty to patient.
So, keep your EMT up to snuff, get experience in sports medicine, get as much general experience as possible, try to get in touch with people doing it now for their experience. Never let a contractor /employer set you up too far above your experience (not training).