They can always find some pretext to deny Polish vessels access
Really? Do explain how Russians can deny Polish vessels access to Gdynia and Gdansk ports. I'd love to hear about that.
And after you've done that, perhaps you can explain where the PISed-up regime are going to find the funds to cut and maintain the channel, upgrade the port infrastructure, build rail facilities and drastically upgrade the road connection. There won't be any money at all from the EU for a project that will destroy a Natura 2000 site.
And when you've finished explaining that, perhaps you'd care to tell us what kind of company would prefer to send goods from Elblag port rather than having them driven for less than an hour to the proper ports of the Tri-city where the goods can be put onto bigger, better and cheaper ships.