Is it possible to punch holes into solids and obstacles which you can go through? In The Games Factory this could be done by "Paste into background" as no obstacle. This lead to two limitations: for it to look convincing, you'd have to have a solid background (with the same color as your hole), and second, it does not get along with screen scrolling.
Does Construct have such feature? I imagine it'd be near impossible because of the textural nature of the renderer, unless it's one big depth write hack.