You cannot have an MSDOS/PCDOS compatible DOS with GPT/UEFI. DOS relies on the PC BIOS explicitly, and beyond the BIOS calls required not being compatible with

You cannot have an MSDOS/PCDOS compatible DOS with GPT/UEFI. DOS relies on the PC BIOS explicitly, and beyond the BIOS calls required not being compatible with UEFI, the MBR is called by BIOS directly as well. On some machines, CSM is enough to emulate the BIOS and get DOS running, but this is not universal at all. More importantly, if you want sound and proper video support you will require an ISA machine or a full PC emulator. If you get into games that are clock speed sensitive, even that won't always be enough.