I don't know of anyway to do that doesn't at least involve overriding
the dialog file for the image component in /apps. By overriding the
dialog in /apps/foundation/components/image you could disable the free
crop, and then you use a hidden x-type to set the crop dimensions. One
thing to consider about this approach is that it locks your default crop
size into the content of the component, so if for some reason in the
future you wanted to change those default dimensions you'd have to write
a scr...