Here’s a modified version of Mr Laforge’s compound that does the extrusion length and inset based on polygon area. Yeah, it uses a Repeat so I don’t think you would use it on a dense mesh and then just leave it in the stack to be reevaluated over and over.

The main idea is that you have to store the polygon indices (and the lengths and insets) before you do the extrude.

See also ICE Modeling – extruding polygons with random lengths