I would also love to know if there is a way to modify the anchor point of a shape.
Take a look at my answer in this thread, you may find it, and some of the methods I discuss, to be helpful. There's also a Guru Session that Mark did which covers this topic.
You may also find this (as of yet unreleased) motion tracking mini-tutorial I've made to be helpful. (It's bundled with another mini-tutorial on alpha masks, but the motion tracking one will be the one you'll want to look at for this particular topic.)
I am researching around and intuitively I would use OPENNI tracker to track my hand and then hook up the motion to the width and height dimensions but, because I don't have a Kinect compatible with the plugin, before I buy it I would like to know if there is a better way, and even if this method can be successful.
If you do end up going the Kinect and OpenNI route, you will want to check out the OpenNI Tracker Tutorial and download the OpenNI Plugins from our Plugin Page.
to change the anchor point of a shape you can use the FFGLPanSpinZoom actor (spin ctrl x and spin ctrl y). It is not a real anchor point but could simulate it.
This plugin doesn't come with a fresh install of Isadora. You'll need to download the TroikaTronix FFGL plugins from our plugin page and install them if you want to use them. Personally, I use FFGLPanSpinZoom all the time because it's more convenient than using both a Zoomer actor + Panner actor + Spinner actor.