Nope, didn't work on my MacPro. I'll read up on the links you provided.
There's always bootpicker or fiddling with my original post regarding the firmware password. It seems that to get to the disk screen without automatically booting to the blessed system folder, one needs to change an option, but I can't seem to make it work. Here are the options for the firmware password:
sudo nvram security-mode="none" // no firmware password
sudo nvram security-mode="command" // standard password mode
sudo nvram security-mode="full" // no booting until typing in password
nvram -p // print screen for settings
I'm not able to make the "full" mode stick. Any suggestions?