There's been a few discussions over the years about the need for a usable-over-ssh binary upgrade tool for NetBSD, but they haven't gone very far. Users ask fairly frequently, and other than sysupgrade, the best method is to implement sysupgrade manually with ftp and tar (and this is required for binary upgrades on some NetBSD ports that lack installer images, so I've had to add it to the official installation and upgrade notes).
I'd like to import sysupgrade into src, since we're basically maintaining it in pkgsrc due to jmmv no longer accepting pull requests (and requiring Google CLA to be signed!), and juggling pkgsrc patches so it keeps pace with NetBSD changes like xz sets isn't most ideal. It doesn't have any dependencies that aren't already in NetBSD, other than shtk, which is small enough as a shell scripting library that I'd simply bundle it with sysupgrade. Other than that it relies on sh, ftp, tar, etcupdate, postinstall, and ATF.
