Yes, there is a kernel-exec support, but that's... iffy. You still have to bring down the entire system to do it, it just saves you from having to run back through BIOS. That wasn't my worry. It was more that the new kernel would fail... that problem still happens if you use kexec.
As for blocking repeated logins, that should be up and going now.
As for blocking repeated logins, that should be up and going now.