Over a dozen years ago I suggested on behalf of Southwark Cyclists a new pedestrian and cycle bridge linking Rotherhithe with Canary Wharf.
Sustrans took this on as a project idea and its sisnce appeared in Southwark planning strategies. But its never quite taken of. Sustrans consultatnts Ramboll Whitbybird in 2008 suggested it would cost £66M capital and £69M to operate and maintain over its 125+ year considerable life time to build at the height of the last boom.
Sustrans employed consulted Colin Buchanan to produce an economic appraisalwhich was last updated in 2008. It suggested such a bridge would result in significant numbers of people changing to walking and cycling to work and for leisure. They estimated 1m pedestrian and 1.6m cycle journeys a year. We know from the wobbly bridge that such estimates are usually wildly pessimistic.
Even so they estimated the benefits at over £236M + potential for £19M secondary revenue without any tourism impact.
They have a design in mind but these are a couple of other ideas to mull over for fun:
The Duisburg Inner Harbour bridge which flexes up and way over any large ship or boat.