I am developing a custom theme for Magento on top of Enterprise and we're trying to use full page cache. We recently discovered that we need some custom placeholders (aka hole punches) in our theme so that Magento can correctly cache and serve up our pages. All of the examples I see for adding additional placeholders involve custom modules or editing core xml files. Because this is a multisite instance with several other unique themes I don't really want to clutter up global namespaces and have a collisions as we grow.
Is there a specific / standard theme level XML file where all fpc placeholder XML should go?