hrm... interface to system/native dialog boxes?

What do people think the best way to allow access to built-in dialogs like file dialogs, font-selection, etc, etc, should work? I don't like the idea of just writing one using the new gtk/glyph support. This would be an interface onto GetOpenFileName() / GtkFileSelection. Should popup-dialog-box be extended, or does a new function need to be written? You could extend the syntax that popup-dialog-box expects by substituting a symbol as the first item in the list (as opposed to a string). The rest of the list would be a property list modifying the default behaviour of the system dialog (is the file for opening or saving? font choice restrions? blah blah blah). -Bill P.