We’ve had far smaller vessels in the past that have been rail enabled though, even smaller than what we currently have.
An argument against moving is we wouldn’t just have to build the port, we would need road, rail, and all the utilities as well, whereas in Picton they’re already there.
That’s been done in a way with a catamaran service, the Fast Cat ferries were brought in to compete with them. I think they sailed from Porirua.
Part of the problem is you would have to base yourself in Port Underwood, which is kinda the middle of nowhere, which would erase some of the time savings.