So what happens in LSCO when you can't get that helo to come in and medevac your mascal patients directly to Role 2 or Role 3 because the bird will get shot down?
People with injuries that don't demand prompt surgery or resuscitation will probably survive, the others will die.
You either move the patient to the surgeon or move the surgeon to the patient.
Easier said than done.
For all the effort that has gone into creating the forward Role 2 / FRSS scheme ... its success is absolutely dependent upon a 100% secure location to put it, which implies 100% air supremacy and 100% suppression (or absence) of accurate enemy indirect fire. These are things we've had since our threat shifted from Cold-War-turning-hot, to bombing the everloving **** out of Saddam's Iraq before screaming into Kuwait with half a million troops, to chasing insurgents. But we won't have them in a conflict with a peer or near-peer adversary.
These "mobile" forward surgical units really aren't that mobile. And they're hard to hide, and they're fragile. Even a 9-person FRSS has an absolutely huge logistic footprint. Multiple C130 aircraft to move all the stuff and people ... which needs a runway. Or a LOT of rotary wing aircraft. Don't forget the people and stuff for security, comms, utilities, even basic manual labor. And don't forget that if things are really that dicey out there on the line, those logistic assets are going to be moving trigger pullers, not us.
With practice and frequent drills, a team can unpack a basic 4-tent FRSS in a few hours and be ready to accept casualties. Packing up to leave is marginally quicker. But it's not fast enough if the enemy has artillery or aircraft. And of course, "ready to accept casualties" might mean only one casualty before resupply is needed (blood being the biggest consumable for these trauma patients).
AND ... it's not like that patient isn't going to have to get CASEVAC'd promptly anyway - role 2s don't have much holding capacity to speak of, and the idea is damage control surgery and prompt CASEVAC.
I spent my last deployment as the OIC for a FRSS parked in Italy as part of a "quick" response team for crisis response in Africa. I learned that there's a lot of magical thinking going on when it comes to the capabilities some folks in the line think a mobile role 2 has.
There will be no moving the surgeon to the patient in the next non-insurgency conflict. We will either move critically wounded casualties to secure locations promptly or they will die.