Do you want a mayor who will bring about a revolution in London?

As for this

Imagine a minimum wage, two job cleaner living on Rotherhithe. If they work in Canary Wharf, they're still taking cycle/bus/tube/train the long way round because an extra £750 a year wouldn't be an afforable expense, even if the boats are bigger and carry more bikes

I agree with you regarding lack of provision for this demographic, but those in charge of London have already shown that they are happy for such people to bus in from the depths of Zone 6 so that people's toilets can be cleaned. They are not about to build them a bridge, not unless there's some 'regeneration' kickback.

You would be better served sinking money into a discount Oyster scheme for low-paid workers than another 'flagship' project.