I’m not sure if this was already present in Cubase 6, but Cubase 7 has the ability to export (one or more audio/midi/group whatever) tracks to a ‘track archive’. From the manual:
You can export Cubase tracks (audio, FX, group, instrument, MIDI, and video) as track
archives for import into other Cubase (or Nuendo) projects. All the information
associated with the tracks will be exported(channel settings, automation tracks, parts
and events, etc.). If you select the “Copy” option (see below), a separate “media”
folder will be created, containing copies of all referenced audio files.
Again, not sure if this applies to Cubase 6 as well, but perhaps this could be worth considering an upgrade for. It’s been a very useful tool for me indeed!