You could use the man-in-the-middle technique. Instead of pointing the iframe directly at the intended target, point it at a page on your server that:
Retrieves the requested URL and injects the script.
Rewrites images and other resources that have relative URL's to use absolute URL's that point to the source.
This is messy and error-prone.
Alternatively, if you have some sort of HTML renderer on the server, you could retrieve the document, parse it, and query for the height. This is messy, slow, error-prone, and not cross-browser compatible.
I think the real answer you are looking for is, no, there is no reliable way to achieve this effect without cooperation from the cross-domain resource.
