Seems to me the only effective and enforceable redundancy that can be easily be imposed by regulation would be mandatory tug boats.
Which there are in some places. Where I grew up I'd watch the ships sail into and out of the oil and gas terminals, always accompanied by tugs. More than one in case there's a tug failure.
Way it worked in Sydney harbour 20+ years ago when I briefly worked on the wharves/tugs, was that the big ships had to have both local tugs, and a local pilot who would come aboard and run the ship. Which seemed to me to be quite an expensive operation but I honestly cant recall any big nautical disasters in the habour so I guess it works.