This came up this morning... wondering if possible:
A render element that would do a material override on all (or chosen via a list) objects in the scene and apply a simple grid over them, tron style, with a customisable scale (such as 1m, 0.5m, 10m etc.). Just a simple b/w mat.
This would be a cool little tool to help with perspective alignments in post, such as placing people over a large surface area etc.