The commission did a good job, in my opinion, of putting forth the options for policy makers need in order to make the best possible choice. They had to consider the new technologies needed and the budget constraints that would be relevant in making those choices. Here are a couple charts which shows what the committee was reviewing. They didn't recommend any particular one of the options, but what they did say was that Mars was not the best first option, but it was the ultimate option.
|Refueling the external tank?|
|Titan/Delta hybrid "Heritage" Launcher can be refueled?|
In summary, I would prefer a flexible path (Option 5c) with a deferred schedule to Mars. Before going to Mars, a better launch system than these should be developed. A two year mission is too long. The procedure required is too complex, which invites critical errors in my opinion. With a mission like this, there is no margin for error. That makes the mission too vulnerable to failure, which would be too great of a risk.
Update: I think I should add one more speculation on this proposition. Can the SDS (shuttle derived system) be refueled? If it could be reused again and again, that would be better than discarded it the way they do now. That big external tank can hold a lot of stuff and could come in handy in space.