Tabs

This is tab 1. Let's see if we can do this and still maintain normal control over adding content. 

Nope, that didn't take long to rule out, as format needs to be:

<div class="tabber">
  <divs class="tabbertab" title="Tab Title">content</div>
</div>

But in the editor, for blocks to be editable/addable, they need to be direct children of a generated div called "ui-draggable". System clash.

One way I can think of to make the tabs concept possibly work is to use special marker blocks and some javascript trickery. Drop a "start tab" block, it has block options for move and delete only (should you be able to duplicate??). No background tool, no block options tool, but instead a tab icon which opens a basic dialog for entering the Tab Title. That's it. Everything after it becomes part of the tab content, until it either hits another "start tab" block, or an "end tab set" block. 

On page render, the javascript would find the first "start tab" block and replace it with:

<div class="tabber">
  <divs class="tabbertab" title="Tab Title">

Then the following content divs would be contained inside that one tab.

When it comes across the next "start tab" block, it's replaced with
  </div>
  <divs class="tabbertab" title="Tab 2 Title">

And so on. It ends the tabber either when it finds an "end tab set" block, or when it reaches the end of the page content (excluding any preFooter content).