There is no way you can control the way google render the maps dynamically, the only thing you can control is the scatter plot above the text object. Probably the most fancy thing you can do is change the color of the bubble that is drawn by QlikView. Let me tell you that we found about these a few months ago, so we decided to start our own development. Currently we have something similar to what you see with the google maps integration, but using the clients geographic information, such as shape files, postgis databases, rasters and more. The way the polygons are drawn is on our own control, using xml files, called Styled Layer Descriptor(SLD).
In the case, our development may help you, please contact me at firstname.lastname@example.org