Ok, here goes my stupid idea:
Duke, IIRC you're trying to help the poor aliens get out of their UFO, instead of crowding in some place inside and get slaughtered by through-wall weapons, right?
Forget about inside/outside -- even if both sides are outside (or inside for that matter) they could still be lured to the other side of a wall or some other large (and concave) obstacle -- instead, if they can shoot their intended target from their intended destination good, if not, use the routing/pathing system to check how long they'd need to walk form their intended destination to the target position, and pick the one with the shortest route (yes, I know its probably extremely costly, stupid idea I said), maybe have them prefer destinations from where they can shoot their target but cannot walk to it (they probably have some sort of cover).