Render object regardless of depth (always render)

I have a system set up where I encapsulate objects within Cubes (via some python scripts, so that when I export a model I know which vertices are inside of which Cube). I want to draw the Cubes (in preview) regardless of their rendering order, so that if the Cube is inside of a mesh (like a building, for example) I can still see the Cube.

Is this possible?

Is there no way to do this? I basically want the “X-Ray” option like there is for Skeleton’s, only for arbitrary boxes that I attach my own attributes to. Perhaps some trick with layers or something…?