This has come up on a number of occasions. There are enough things people want to customize that, rather than adding options for each such detail people want to customize, we'd prefer to have a general mechanism for new template projects, which people can add to and share.
That's exactly my thought. While I want publish = false, that doesn't mean others do. I'm fairly certain there's a crate out there that allows custom templates, but I've never used it because cargo init / cargo new is so ingrained in my head.
Having something in ~/.cargo would make sense. A directory that would be cloned, replacing a couple placeholders as appropriate shouldn't be that hard…right?