Yes, this would be a much better architecture, but unfortunately, while Buzz is probably the most famous moonwalker, he’s also not taken as seriously by many in the industry.
Two comments: I’ll have to ask Eric where he gets the $1.5B/flight number for SLS. And is he proposing to do this in the ISS orbit, or at a lower inclination?
[Update a while later]
Meanwhile, Bob Zimmerman reports that NASA is preparing us for another SLS delay.