There is no such facility because the value of the ContentAreaMode property changes the rendering of the RadEditor, and a client-side feature has not been implemented yet. I can suggest you add your idea to the Feedback portal and if it gains enough traction in the community, the product management will review it: http://feedback.telerik.com/project/108.
You can look into initiating a partial postback to toggle the property on the server.
As for the use of the get_contentArea() method—it provides you with a reference to the editable area object. You can changes styles, content, traverse the DOM of the current content.
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