The facial tattoos and scars are textures on the character model, and they wouldn't flip if only the animations flipped. Don't think the hair would either. The weapon most likely would, though, because its position is part of the animation data, unlike the character's textures. Hair animations are (well, can be if turned on) animated with realtime physics so that likely wouldn't be affected either, or it would be easy to make it not be affected.

With character models+animations flipped, things like reaching out for items would look off, but many of the cutscenes where things like that happens, the characters' hands often don't actually touch anyway. Maybe a minor manual edit to such cutscenes would be enough, such as turning the character a few degrees to the right when they were going to grab the item.