another thought… generate>Vegas… add to png change to image contour and use alpha. Fiddle with settings to get it to be one line and then you can use length as a trim. The only issue I see is that it creates the ‘stroke’ on the inside of the alpha but maybe that’s not an issue! hope this helps
maybe… use auto-trace, then use that mask to create a stroke (generate>stroke) use that to trim stroke, apply the layer style to the new stroke and it’ll draw on and off
*Correction… I forgot about the division on the face, you will need to do that process on each 5 sided shape, and have preserve groups on within the inset tool. and use the collapse command to merge the new points together.