Still not perfect, or fitting exactly what you want to do, but I KNOW* many people use, is second point in 8 on:

http://www.nearby.org.uk/google.html#8

This will maintain a circle in the center of the view. As its a network link you can open multiple copies, and each one has a configurable colour, and also radius (right-click and choose properties, and edit the URL)

So in your case setup a number of links as required, then move around the earth, and when the circles are as you want them, just Copy the placemark(s), and paste it into a folder.

As I say still not perfect, but possibly easier than copy/pasting all the lat/longs and setting the variables as you need. If interest could add a filled polygon option


* (in fact its almost the most used tool on the website, but that might be by accident, anyway I digress!)