Editors choose layout I want to give editors the ability to take advantage of a grid system we have on our site.  I can easily jump into a node and add this to the Body 

&lt;div class="grid-12 alpha omega"&gt;one column&lt;/div&gt;
&lt;div class="grid-6 alpha"&gt;content on the left&lt;/div&gt;
&lt;div class="grid-6 omega"&gt;content on the right&lt;/div&gt;
&lt;div class="grid-12 alpha omega"&gt;one column&lt;/div&gt;
...


Editors aren't savvy enough with HTML and CSS to do this themselves, and that's fine, that's what wysiwyg editors are for, and why we use Drupal in the first place (mainly).  

But, this is a system of layout that can be applied consistently on any node. I'd think it would be easy enough to allow editors to take advantage of it. I'd love to let them create as many rows with as many columns as they want on any node without having to code it up themselves.

I know I can create template files that will apply structured HTML to all nodes of a given type, or one node, or some subset of nodes.  However, I don't want to make that choice for editors.  And besides, you can't split up the body content of a node into rows and columns like that from a tpl.php file.

I've looked into Panels too, but from what I can tell that's just a GUI means of creating tpl.php files.  Same problem.

This is very similar to the unanswered question Select Panel Node Layout on Node edit form.  I'm using 7.
You're asking a chicken and egg problem. Nodes just hold data and no information about the theme (usually). You're describing mixing the two in the Body field of a node, in essence hard-coding the look (layout) of your "node" in the database.

Drupal in many respects fights this as the page content is 1 item and drupal7 cares nothing about whats around it. In D8 their is a UX initiative to make a nicer page layout creation system.

In D7 you may be interested in context_layouts found in Context. See this youtube video on its usage.

I've done something similar (but not Grid aware) using Spaces, spaces_node and Dashboard (spaces dashboard) in Drupal6 per node (I also used node_block heavily). Every node/page could have their own unique layout using Spaces and its submodule of Dashboard; you can set any content to any block/region of the page as needed using a drag-and-drop overlay. Actually, the site I'm mentioning is UCSB SageCenter. Unless your logged in and editing a Space/Dashboard you dont really see anything in the source. I added a node field to pre-assign a known space for node pages on node creation. This site was hard.

Here's a video demo on spaces_node -- its not supported anymore really.