Cygnus Dragon docking demonstration mission
Cygnus Dragon docking demonstration mission; A precursor to a Hubble telescope repair mission
1968 space rescue treaty might call for such missions to be possible.
SpaceX Dragon undocks from ISS to make room for an incoming Cygnus mission; outside the ISS keep out zone both Cygnus and Dragon dock and undock.
Repeat this flight experiment when Dragon crew comes online, can the Dragon crew open the Cygnus hatch? Cygnus here is a temporary life boat for Dragon or ISS crew in some failures modes.
NASA CCiCap requirements should include docking maneuvers between spacecraft.
CYGNUS DRAGON HUBBLE SPACE TELESCOPE REPAIR
Consider a Dragon and Cygnus mission to upgrade the Hubble telescope; there may not be a budget for up graded instruments but this mission could replace avionics.the mission could be a public/private partnership in that Orbital and SpaceX would be partners in a S corporation. possibly other partners such as avionics supplyers.Hubble data is sold over time to recover costs and to provide a profit and interest to the S corporation partners.NASA would buy the data on behalf of the space telescope institute.
EDIT 11 August 2014
I am not sure if the geometry of the Cygnus would allow for a docking with Dreamchaser