I don't think that's fair to Gray or Mckendrick. They oppose what Stage 1 of the Green Line has become and are offering their own ideas. As they say, success has many fathers, failure is an orphan but also with many people saying that they can do better.
IMO basically it boils down to how fast Calgary can get another $2+B for the Green Line. If that money is available prior to the end of Stage 1 construction than building out Stage 1 as is (but with a better river crossing option) is the best option. But if that money won't be available for decades, than it will be a financially draining white elephant and it would be better to prioritize opening-day ridership by going further SE at the expense of the river crossing and other cost cutting in the core.