re: Gotta disagree about the growth capacity of the EELV
Yes, you can slap more solids on the sides to a point. But, if you do it as the CEV grows in weight then I believe you are continuously working man rating as you test. This would not be cheap.
The problems they originally used to table Methane engines was the costs and length of time it would take to man rate them. The big dilemma with using "new" second stage engines with the stick was man rating them. This seems to indicate man rating is first still expensive and second time consuming.
An interesting statistic concerning launchers is the rate of failure seems relatively stable over time. This includes new or old launchers. But it is much higher than we seem willing to accept with humans. I think it's something like 1 in 20.