Have you guys looked at this roof on google earth?
The barriers are way out on rails much wider than the pad and the area around it.
But I'm not an aviation professional ( or amateur!) so it may still be tight.
From an engineers perspective, couldn't these be designed with say a 42 degree slope down off the pad for 3 metres then bring the balustrade back up to 1200mm, that way it would be below the level of the pad, but unless you're a free runner, you can't fall off it.