The highest profile challenge to the Docks, if we have secured the site, will be UNESCO but both the council & national government have already made it clear that they will choose jobs/investment over UNESCO status if push comes to shove.
The most common practical objections to large-scale new development typically centre around noise, public order, pollution/rubbish, crowding/transport. They can all be addressed and frankly need to be anyway, irrespective of objections, to make the development successful.
The process would take time but there is a near zero chance that any council or national government will turn down a likely £1bn (taking into account ancillary developments around the stadium) investment into one of the poorest areas in the country. No doubt Reds will moan and try to be awkward but the £ at stake will ultimately drown out the noise.