Multiple select for node types

I'm working on a site where I have different node types that I want to be handled as equivalent, at least in terms of how they are presented to the end user. For example, I have Flashnodes, standard stories, and other types of content that make use of specialized CCK formatting to make life easier for contributors. All of that content will be grouped by date instead of by type, so I need one common set of custom breadcrumbs across all types. Managing one set that is common to multiple content types would be simpler if the select input would allow multiple selection.