Can I restart macOS Sierra in safe mode remotely?
This is similar to Trying to set boot-args with nvram gets &quot;general error&quot; on Sierra. I have the same situation - you must be in Recovery mode to set nvram variables, so you cannot start in Safe Mode remotely, unless you have disabled SIP.

I've been able to set nvram variables remotely after disabling SIP (csrutil disable), but disabling SIP requires you to boot to Recovery mode.

However, if you have something like DeployStudio in your environment, you can:
1. Create a DeployStudio workflow that runs a simple bash script to disable csrutil
2. Configure your NetBoot set to auto-run that workflow for that machine
3. Configure the machine to reboot to that NetBoot set and reboot to kick things off.