@jfred @cwebber
Yeah, kexec exists, and "guix system reconfigure ..." even generates a kexec script to reboot without going all the way into the bootloader... and sometimes even suceeds!
Maybe for some systems it is quite reliable; I have had mixed results, so not sure I would want to rely on kexec without a lot of testing...
Off the top of my head, petitboot implemented a "boot to minimal linux and kexec to full system" sort of interface... there may be other projects in this space as well.