Please review the following case and let me know if I am tackling the problem with the “best” solution.
Our business users can create “Form” content items that are inserted as a snippet into a publishable page. Business users rely on external form services such as Wufoo and FormAssembly for form processing and data management; therefore, these content items contain a URL to the published form. The snippet template creates an iframe pointing to the content item’s URL. This solution is not suitable.
One possible solution may be to create a JEXL extension that will allow the snippet template to call a Java class that will retrieve the external form code, as well as perform clean-up.
Another solution may be to create an item input transformer that will use the URL to the published form, and upon create/update it will retrieve the external form code and save to another field within the content item that can be referenced by the snippet template.
As you can see the main goal is to step away from the iframe solution.