Yea we know about the licensing for this.
After reading your notes about versioning, we confidently think we can determine the ACF version minimum requirements, and if the plugin is there and the minimum version isn’t >= our needed version fire up an admin_notice.
I think the ultimate answer lies in using exported code and avoiding the DB for addding fields to the custom post type.
Looking at http://www.advancedcustomfields.com/resources/register-fields-via-php/ seems to be the right direction. Does exporting to PHP (or json) prevent end users from manipulating the fields?
