Updating this for macOS Ventura...
The OP asked about accomplishing this in Sierra.
TLDR It's likely the only boot-arg
permitted (even with SIP disabled) is boot-arg="-v"
for verbose boot.
I booted a MacMini2 2023 into recovery mode and turned off SIP:
[-bash-3.2# crutil enable --without nvram
crutil: Requesting an unsupported configuration. This is likely to break in the future and leave your machine in an unknown state.
Turning off System Integrity Protection requires modifying system security.
Allow booting unsigned operating systems and any kernel extensions for OS "MacMini HD"? [y/n]:n
csrutil: aborted
Then shutdown...
shutdown -h now
and booted back into Recovery Mode and tried to supply 3 different boot-args
[-bash-3.2# csrutil status
System Integrity Protection status: disabled.
[-bash-3.2# whoami
root
[-bash-3.2# nvram -d boot-args
[-bash-3.2# nvram boot-args
nvram: Error getting variable - 'boot-args': (iokit/common) data was not found
[-bash-3.2# nvram boot-args="-v"
[-bash-3.2# nvram boot-args="-x"
Error setting variable - 'boot-args': (lokit/common) not permitted.
[-bash-3.2# nvram boot-args
boot-args -v
[-bash-3.24 nvram boot-args='-x'
Error setting variable - 'boot-args': (iokit/common) not permitted.
[-bash-3.2# nvram boot-args="-s"
Error setting variable - 'boot-args': (lokit/common) not permitted.
[-bash-3.2# nvram boot-args
boot-args -v
-bash-3.2#
Unless someone has another idea looks like we've hit a roadblock.