Cross Domain policy with AJAX multiple contexts on the cloud

Hoping someone might be able to shed some light on this.

We have an issue whereby we have multiple contexts with multiple domains associated with them and a data structure of resources held on one of the contexts. Currently we are populating via AJAX various modals from the data structure in a JSON format, using a SEO friendly snippet that queries the call and feeds back JSON or the HTML rendering of the resource depending on the request. This all works fine within the context the data is hosted in, but when requested outside the context we get the usual cross domain issues.

One of our solutions is to add a Cross Domain Policy allowing the other domains in. I am pretty new to NGINX and have been trying to get a policy in place. Are there any caveats in the MODX cloud which I have to consider or has anyone had any success with this?

Other solutions we have considered involve trying to mirror/route the data structure on the other contexts. Opinions? I realize this could throw all sorts of routing problems our way and could be poor on the SEO side of things with duplicate content.