In reply to Garry HJ.

Also, the idea is to show not just what the button does but what the effect looks like BEFORE it is applied to the page, therefore the site preview is not the requirement and does not provide the solution sought. The graphic on the button does it far more clearly.

I'm going to have to disagree with you on this one. A live preview shows you exactly how the change will look, on your site with your configuration, before being applied to your site. A static image graphic is a poor substitute.

Flyouts? Pfftt … several people I know would immediately refuse the solution if they had to make use of such frippery. They want basic and solid, at-a-glance, blocks of options, not gizmos for spotty teenagers. We are of course talking about corporates here, though it also applies to sole traders and family businesses.

I doubt corporates are using directory-hosted Themes, out-of-the-box.

Unless you can offer a customiser format where the page is the options and the preview is in a sidebox, you are asking everyone to accept a massive paradigm shift in site admin, and will lose a lot of supporters and users due to it.

And yet, that's the direction that the core development team has chosen to take. Besides, the WordPress admin has undergone massive changes over the past 10+ years, and somehow the platform has survived.