"a heavy lift expandable launch vehicle would lift the spacecraft into high Earth orbit"
http://spacescience.nasa.gov/missions/JIMO.pdf

I'm wondering what type of a 'heavy lift launch vehicle' they will use. The Centaurs worked very well for both the Pioneers and Voyagers and they definitely used celestial mechanics for both missions as well.

Pioneer History

Voyager Missions

Focus on the Future

Project Prometheus would enable the fulfillment of NASA’s most challenging scientific goals, and will provide the essential ability to answer our most intriguing questions: Is there life elsewhere in the Solar System? How was the Solar System created and what is its future? These questions can be answered when we are able to explore--with enough time and power-enabled by the ability to change course in mid-mission to take advantage of the opportunities presented by new discoveries. Providing these important capabilities is the focus of Project Prometheus.

From: spacescience.nasa

The part about "-with enough time and power-enabled by the ability to change course in mid-mission" sounds pretty good and should definitely be tested.