Not a common sight. Would like to see the picture so I could build one and not get beat up at a local show by those who revel in accuracy.
I fly CASEVAC with the USMC and am the Navy liaison instructor at the Army Flight Medic Course. With the USMC we are considered combatant aircraft and do CASEVAC from the frontlines as a "dedicated" platform, not a "designated" air ambulance. That puts us into a lift of opportunity or CSAR status and we can carry weapons (.50 Cal.).
As I am sure you know, the rules for U.S. Army designated air ambulances are no weapons if they are identified as such with a red cross. No good deed goes unpunished......Good old Geneva Convention!