I\'ve been using the default theme with about 10 faces changed via
custom-set-faces for a while now. But from time to time I want to
try out a couple of the custom
It seems that disable-theme does what you want.
UPDATE
Here is one way to get the 'default theme template'
1) Disable any additional theme (using disable-theme)
2) Invoke the command customize-create-theme it will open a customize interface, which lists all the default faces, which you can customize and create your own theme
If the customize-create-theme is called with theme name it will list all the faces that are set by the theme.