You can use a BIOS with GPT (which remove partition size limit using LBA48) : see EDD 4 page on 4 https://www.fpmurphy.com/public/EDD-4_Hybrid_MBR_boot_code_a... : "Hybrid MBR boot code overview: This annex describes how MBR boot code called hybrid MBR boot code may be constructed to support a GPT disk layout (see UEFI-2.3) in a legacy BIOS system."

I'm working on that for one of my projects. A BIOS can use GPT partitions to have LBA48, but MBR partitions standards could laso be changed to use LBA48 instead of LBA32 which cause the limit

You could even use the CHS fields to have even more space if needed: there are 3 bytes for the CHS start, 3 others for the CHS end, both are often wasted by storing 0 for LBA32.

That said, I still consider UEFI to be better for at least 1) multiplatform support (have different /EFI/BOOT paths to payloads named by their architecture) 2) fallbacks (shell + startup.nsh) 3) defining how the persistence of settings work (efivars)