Okay, this is not tested, only passing observation, but it seems to me, if I Hide the guys doing the buddy aid, they will be treated as prone, even though the animation shows them kneeling. I was upset at times when my guys would do the buddy aid thing in clear sight of the enemy, so I started putting them on hide as soon as possible. Also, when I deliberately want to send them to give aid, I have them Slow/crawl to the person, and make sure they have Hide orders. Seems to work. I've had guys buddy aid within 2 or 3 Action Squares from the enemy (but usually behind cover or concealment), and they are neither spotted nor fired on...usually.