That doesn't seem like a large-scale solution. You could get it to "work," but what if other people view the site? You can't force everyone else to also use an apache proxy... I'm sure there's some detail I'm missing here, but if you can't get the standard ebay.com to do it, how does it help?
Proxying in general is a very large-scale solution, and it is the only secure solution to this guy's problem. Proxying it through his own site will place the remote site "in domain" under his domain and make the iFrame fall naturally under the "ORIGIN" access control which most browsers (and Scirra's export) operate on.
You don't need to 'force' anyone to use a proxy. You set it up for yourself and it simply funnels traffic through your domain to another site and back. Think of it like a tunnel from your server to the site of interest.
I actually use this exactly to get our blog site to run in an iFrame on our website.
interesting, can you show example?
Look at our website and blog. Or do you mean a Construct example?
I do like gamecorpstudio 's solution too.