Multiple taxonomies in single field
You can try the Computed Field module.


  Computed Field is a very powerful CCK field module that lets you add a custom "computed fields" to your content types. These computed fields are populated with values that you define via PHP code. You may draw on anything available to Drupal, including other fields, the current user, database tables, you name it. […] You can also choose whether to store your computed field values in the database with other content fields, or have them "calculated" on the fly during node views.