In reply to Marc.

There is nothing stopping you from doing that now. You do not have to give control over the design to your clients.

I am happy to talk specifics and help out where I can if you run into an issue -- I am a developer too. If there's something I don't know, I'll try to find out or find someone who does know. Seriously, shoot me a message at justin@wptavern.com or on WP Slack @greenshady anytime.