I wonder how you’re supposed to get PXE boot to work securely over the internet.
PXE boot is more of last resort IMO, but can be uses as a chainloader to a more secure option. The biggest challenge I could see security-wise is having PXE boot being ran on unsecured networks. Even then though, normally a computer will have been provisioned on a secure network and will have encryption and secure boot-based encryption, and some additional signature-based image verification.