That is a pretty awesome idea...
...but it's pretty unfeasible (at least for that particular area). Any bridge like that would have to connect two densely populated areas. Sure, the future SoWa area will be densly populated, but the Eastside probably not. And then there would be conflicts with river traffic.
As for Vancouver, I think you guys could build some sort of mid-level bridge between Granville Island and Yaletown that could contain a pedestrian mall and a streetcar line. Maybe there could be a similar bridge between the Waterfront Station and Lonsdale Quay.