You could potentially map them both as multi-polygons. Two multi-polygons can use the same outline way(s). This would not capture which is on which level though, that would require either a node or a way with the relevant level tags.
You could potentially map them both as multi-polygons. Two multi-polygons can use the same outline way(s). This would not capture which is on which level though, that would require either a node or a way with the relevant level tags.