re: I'm not as concerned in the short term about dropping the methane engine requirement
They as I understand it are working with Block I, Block II and Block III pretty much as you stated.
Block III is Mars and beyond.
The important things to focus on are the abilities to be on station for months and carry the required number of crew members in block I. I don't disagree with Bell on one point. The STS should be shut down ASAP. But, we do have the ISS to finish and nothing can carry the hardware needed right now but the Shuttle.
