Editing 'title', 'body' and 'page number' place holders - Keynote 6.0

Through a progress of evolution we've developed our standard Keynote theme by editing & reusing existing decks. Now we want to create a theme. Easy eh? Just create a bunch of blank slides and save as a theme.

The problem is, none of these hand added elements are designated as 'body', 'title' or 'page number' by Keynote. So when you apply our theme to any other deck none of these elements are properly formatted.

Digging into this a little, the only way I can find to create one of these official placeholders is to tick a box in the Master Slide Layout inspector, which creates a brand new element. Now I've got to manually copy *all* the formatting across from the previous element, position it and delete the old one.

If there was a slower way to adapt an existing presentation into a theme I can't think of it. I must be missing something here. Is there a way to designate a role for an existing placeholder? I've searched and searched and can't find anything.

Thanks in advance.