Hi @Thomas
Thanks for the feature request, however I’m not sure how this could be added into the core without bloating the settings UI.
Perhaps this would be better left as a custom JS script?
The following tutorial shows how you can listen for an acf/setup_fields
event and run JS on any new HTML added to the page via ACF.
http://www.advancedcustomfields.com/resources/tutorials/adding-custom-javascript-jquery-for-fields/
You could look at the input value, and then append it to the layout handle.
Thanks
E