[fredinno]

Is the track elevated?

Also, I don't know if you really need a 2nd skybridge. Skytrain tracks are not capacity-limited by headways on the tracks themselves, but from loading speeds on the stations.
You can pack a *lot* of trains onto a single dual-track rail bridge, even with 60s frequencies on the Expo.

Also, the Skybridge has a rail between the 2 Skytrain rail lines I presume is used for maintenance. Maybe that could be dug up and converted into a Skytrain track?