Crush Coaster is actually an off the shelf model with the dark ride portion added to the beginning. This is what the coaster portion actually is:
http://www.rcdb.com/2164.htm?p=10586 . Its made by a german company (actually the same one that did Rip Ride Rockit at USF) as opposed to a cheap french company for Primeval Whirl.
Disneyland Paris is not happy at all with what the german company delivered. As I mentionned, its a off the shelf version designed to run 6-7 cars at once. Crush can run over 12 cars at once and factor in the year round operation and you got a ride that aged 3 to 5 times faster than what it was supposed to be.
The multiple breakdowns come from a silly mistake on the part of Imagineering and the company. They wanted the dark ride to be silent and not have noises from the pusher tires normally used... So, they made the dark ride portion to run on gravity with a brake zone in the middle of it. So, the result was that each cars run at different speeds in it, based on weight and the wheels, so a faster car would catch up to a slower one and cause the ride to automatically e-stop.
The restraints will require to be modified or changed. The current lap bars on Crush won't allow many people over 6'2 or with large legs to close the lap bar properly.
The loading area would have to be longer or will need a moving walkway like Haunted Mansion. The smaller european guests already have enough problems loading the moving cars, so I can't imagine the guests at WDW doing it without stopping every other car or falling down!
Capacity of Crush is around 700-800 guests an hour on a good hour with little stops and every seats filled. They tried fast pass and it was a complete disaster!