It would be especially helpful if the ID of the content block that's chosen could be passed in as a class (e.g. class="content-block-1412").
Use case: I've got several content blocks I use in several different sidebars. I'd like to be able to define the style for a specific content block wherever it appears, but every instance of that content block widget gets a different ID. The classes, on the other hand, are too broad and every content-block widget gets the same class.