However, I was not aware that kbrequest needed a special ioctl call before it can be accepted, so thank you for that; I'll add the call to s6-l-i.
Scratch that. s6 never uses /dev/console as input: s6-l-i redirects stdin to /dev/null. (This is intentional, and is not changing.) So there is no fd to call the ioctl on, and no way for a user to trigger a kbrequest. A minor inconvenience compared to the advantages of not having any /dev/console input. CAD still works because it's treated as a special event by the kernel, not something that's tied to a fd receiving input. -- Laurent