A recent Government Accountability Office (GAO) report has cast doubts on the ability of the Orion MPCV to meet its requirements on its already excessive budget. Orion has been in development since 2006 and will likely continue until 2023 with costs in excess of \$20 B before crew fly on it.
As I understand the commercial crew contracts SpaceX is to receive up to \$2.6 B and Boeing is to receive up to \$4.2 B for design development and testing of the Dragon 2 and Starliner. So what I am wondering is what modifications would be needed to be made to these spacecraft to let them fly beyond LEO say to cis-lunar space. Necessary modifications I can think of include: life support systems to allow longer missions, radiation protection for crew and radiation hardened electronics, larger heat shield to allow for much faster reentry, and more robust structures for greater g-loads upon entry. Would it be possible to modify the current designs to include these requirements or would these changes require the the development of an entirely new spacecraft which would be about as expensive as the Orion?