image overlays vs. polygons idea revisited

I played around with the idea of using image overlays to create the pies vs. using polygons.

Overlays
Pros: In GE you can easily grab and move, resize, or rotate the image. This way, the user wouldn't totally be reliant on our application to manipulate the pie charts.
Cons: The images could get ugly if increased in size by too much. Also, we'd lose the ability to turn different aspects of the pies on and off (like the labels, particular haplotypes, etc.). And we wouldn't be able to change the colors of the different pie pieces without returning to the application.

Polygons
Pros: There's a lot of information retained in the file hierarchy. The user can turn various components on and off and recolor them easily. Plus, the image is likely to be crisper.
Cons: The user cannot move or resize the pies without going back to our application.

I think that having the ability to access the components of the pies (haplotypes, labels) easily outweighs the hassle of resizing and moving. To get around the hassle, our program will have to have some sort of collision detection mechanism, and some easy way to resize pies. Can we preview the map on google maps before exporting to GE? and allow the users to change things there? That may be the best work around. So I'll continue down the polygon path and leave behind image overlays.

Another thought on overlays: It would be nice to have a species distribution overlay function, where the user uploads an image file with the species distribution and can stretch it to fit the map. Also, I wonder if someone's already made overlays or paths of things of common interest, like where the ice margin was at the LGM, or if there's a repository of species distribution data.