All the years that I lived in Manitoba, the viability of Churchill as a port was always a major political issue for the governing party. The key problem has always been a question of how do you make it an enterprise that provides a reasonable, or any, return on investment to its operators (and those of the rail line leading to it). The answer was that you couldn't. Any business model was always dependent on massive subsidies, grants or whatever from both provincial and federal coffers.
Here's and
article from just before the rail line shut down that highlights the issues.
Regardless of the commodity to be put through the port, the limitation will always be its actual shipping season. Betting on global warming to extend the season is a mug's game if one considers that the world is spending trillions of dollars in trying to stop that very same global warming. To count on a longer open season is gambling that the world will not succeed. Maybe that's a reasonable gamble but regardless, whatever money is spent on building and maintaining the infrastructure (note that I am not saying making the port and rai line self sufficient) could be spent on our ice-free coasts to create year-round terminals that will provide profits for the economy as a whole.
I generally like having a vision for things that we could and should do. Churchill isn't one of them.
$0.02