sfdc/ mc from gravity forms… with admin approval?

Yes, it is possible — there are a ton of places you can hook to action/filters:

• Intercept the ‘use-form’ determination with a low priority value (< 10) to completely prevent the plugin from attempting anything. See https://github.com/zaus/forms-3rdparty-integration/blob/master/forms-3rdparty-integration.php#L406. You’ll have access to <useit?>, $form, $service_id, $service['forms']
• As mentioned in #5 of the “Hooks” section at https://www.ads-software.com/plugins/forms-3rdparty-integration/other_notes/, the “usual” place to check is with the hook service_filter_args at https://github.com/zaus/forms-3rdparty-integration/blob/master/forms-3rdparty-integration.php#L478. There you have access to $post_args, $the_service_config, $the_plugin_form, and if you return an array with response_bypass key it’ll treat that value as the submission response.

If you need anything custom, please contact me through my website.