Need help with custom / self ending tags

I've seen dozens of posts requesting the ability for custom tags, but I can't find any solutions. I took a look a the plugins for pagebreak, and fakeobjects but this seems very complex for what I am trying to do.

Basically I want to be able to edit template HTML content that will be used to generate an HTML email. This template email contains many tags of the form <customtag>. I would like to prevent CKEditor from trying to adding closing blocks for these tags as they are all self ending. Is there any way to add to the list of tags that CKEditor knows are self ending? I saw a reference in the dtd.js file called $empty, but I don't see a way to add my custom tags to that list.

These custom tags are all replaced by a token engine before the message is sent. For a first cut I just need CKEeitor to ignore them. Long term it would be nice to train CKEditor to understand these custom tags, and perhaps display them in the editor in some format, perhaps a colored <customtag> notation, with a button to add all of the custom tags it knows about. All the while the actual html source would just have the raw <customtag> in it. I don't see any examples of this in my searching and digging into the code so far.