The only way to have the pin at least a bit of a hurdle, is recompiling B9S yourself for changing the priority. If CTRNAND has the priority, the only way in without the pin is ntrboot.
Yes, I tried it and it works.
I wouldn't recommend doing this for several reasons:
- Luma3DS screenshot functionality
- Access to game patching
- failsafe: Any problem with the files on NAND → only ntrboot can save the console (a corrupted boot.firm sometimes makes B9S stop and turn off instead of trying the other location)
- It won't stop a dedicated attacker