I added it to the EditForm for the wiki page, and it works great. Unfortunately, the CreateWebPage is where it would find the most usefulness.
I cannot find anything online on how to force that page into edit mode, as it appears to reside outside the list in the _layouts realm.
Edit form lives: /sites/etwiki/Wiki%20Pages/Forms/EditForm.aspx?ID=2
Create form: /sites/etwiki/_layouts/CreateWebPage.aspx?List=%7BC298E5A9%2DA899%2D4840%2DB12B%2DBB6BF7EBCB0E%7D