It won't pay off too often, depending on the mission being run. But as long as he doesn't skimp on his other combat skill trainings, he should be fine. The real trick is preparation - a lot of teams will just kick in doors. Others will allow this guy to prep his charges in advance. I'd recommend for this guy to pick up at least one of the gun skills and Throwing Weapons (for grenades) in addition to Demolitions and First Aid. Medicine will be next to useless, and unless he was an actual doctor or nurse at some point in his story he'd probably only have First Aid anyway. Military medics are essentially combat-trained EMTs. Lifesavers to be sure, but they can't possibly perform surgery under most conditions.
Bullets & Bandages has a great section on how to create a good field medic character, and the points made in that section are applicable to Missions games too.