Support for custom ftl email template files

I'd like to be able to define a .ftl file resource as the email template for a form.

Currently I can only use the default easyforms_html.ftl file packaged in the plugin jar or input a complete template as a parametervalue for parametername 'ef-body-html'

Ideally I would like to be able to define a parametername, e.g. 'ef-body-html-file', with the path to the file as the parametervalue.

Disscusion about this subject on google groups:
https://groups.google.com/forum/#!topic/hippo-community/IIBAom9DzdQ