Thank you Boris.
Okay, so based on the list, here is a modified version of that suggested code. Add this custom code to the functions.php in your theme/child theme directory (copy from line 3 only!). Before editing, please make sure to have a full site back-up just in case!
The newly created custom fields you can add to the $field_names variable. This should also handle non-relationship and non-repeater fields as well. The repeater sub-fields should be automatically converted to non-arrays. There is still a chance that this may not work, as repeaters and relationship fields does not have a fixed structure, but I think this is as close as it gets.