You can stylize that with css on the backend, choose the mode block, and them create .css file on your theme, then “link” the .css to the backend, after that use the “Inspect” on safari/chrome/firefox to see the div’s and starting coding the css. In that way you can modify to look like “standard layout mode like any other field group is rendered”.
And the ideias about collapse and drag n drop features i totally agree on making this. =D
