A lot of that seems really implausible to me. it seems as if these rumor are from a VERY blue-sky POV, if they're genuine.
Logistical nightmare is exactly what I was thinking about as I read the article. There's no way in heck they're going to have being loading and unloading inside an attraction. I just can't see it. You've got people with children, people with handicaps, heavier people, older people, people carrying bags. It looks bad through so many lenses - logistics, safety, ride flow, capacity, bottlenecks. The article mentions some sort of elevator system IIRC, if vehicles are moved between floors perhaps this is the mechanism they're using to do so.
The numbers
@TheMaxRebo posted help put the capacity talk in context. I believe they will be on the higher end. They're building their newest, biggest and best in what will be an insanely popular land installation - how could they not consider capacity to some degree.
A prediction regarding Big Bird - the option of failing your mission, or not getting a happy ending like the article suggests, will not make it to final stages OR will be removed/made optional due to guest dissatisfaction. Regardless of how simple the tasks you have to complete are, people will mess them up. This is still Disney - happy endings are the pretty much the whole point. "Oh sorry little Timmy, your failure destroyed the galaxy. Have a magical day!"
A lot of these things sound like ideas that could have initiated the WDI shake-up that happened a while back. Just speculating obviously.
All that being said, getting these little tidbits is incredibly exciting, and overall I can see a lot of potential with these attractions.