re: I agree. The surest way to kill the program is to try to design a one size fits all vehicle on the 1st go-around.
I'm no rocket scientist, but to my untrained eye going to and from Mars will take much more than a CEV with the proper L/D ratio.
I agree that we need to begin thinking about these things now, but we can engineer for the moon now and complete the engineering for Mars later as we near the actual Mars mission.
By reinventing the Lunar return vehicle we can both learn from our previous successes and mistakes while also incorporating newer technologies into the design (and we might even develop yet unseen technologies in the process of redesign that might make any Mars return designs of today completely obsolete tommorrow (ie. 10 years down the road...)