In support, and defining LOAC to those that do not know much about the military (particularly US as that's where I'm basing my knowledge from), LOAC is Law of Armed Conflict. The general rules of combat as it is imposed on any fighting force and is to be upheld. Doesn't always work that way but at least there are rules.
In LOAC, medical personnel must be marked with the corresponding symbols such as the red/white cross. At which point they are non-combatants and cannot be fired upon or attacked. Rather, they aren't supposed to be. However, if they pick up a weapon, they become combatants so the trade-off for that combat immunity is that you cannot defend yourself without losing said protection.
I do believe though that combat medics can be armed from the get-go and as such, don't wear clearly marked medical personnel items on their person. They just become normal combatants who treat the wounded. And in such small units, you know who the medic is anyway. So it's not like you need to figure out who the medic is by putting a big sign on them.
Problem in war is that (as I said) the other side usually doesn't care about LOAC. So they're going to shoot a medic. If I were the enemy and could care less about LOAC, heck yeah I'd kill a medic. It's a smart move. Shoot at someone that can't fight back and fixes my enemy's troops. It's a no brainer.
Of course, I think I'm getting WAY off topic here so I'll steer it back on point.
In the Halo world, you're not fighting other humans or something like that. Even though ODST is cited as being used in human vs human operations. The application is mostly against Covenant who want to exterminate the entire human race. So honestly, such a thing as LOAC goes right out the window. ODST are nothing more than another slab of meat to be shot as far as they are concerned. Taking into the context of the circumstances, if I were a field medic trailing the ODST, I probably wouldn't want to be marked just for the sake of not sticking out in the crowd. Even though I'd be armed and whatnot - it's just never a good idea to be a beacon for snipers and the like.
But, I doubt the OP is going to be using this armor to go out in real-world combat operations. And the only way to really make the armor "medic" brand ODST is to label it as such. Otherwise they could just take a standard suit and say "I'm a medic" which is no fun.
So I say, brand away!
