The idea with Limine is to remove the responsibility of parsing filesystems and formats, aside from the bare minimum necessities (eg: FAT*, ISO9660), from the bootloader itself. It is a needless duplication of efforts to have bootloaders support all possible filesystems and formats, and it leads to massive, bloated bootloaders as a result (eg: GRUB2). What is needed is to simply make sure the bootloader is capable of reading its own files, configuration, and be able to load kernel/module files from disk. The kernel should be responsible for parsing everything else as it sees fit.
Simply put, this is unnecessary. Putting the kernel/modules in a readable FAT32 partition and letting Limine know about their BLAKE2B checksums in the config file provides as much security as encrypting the kernel does.
We have. While this is a pointless effort on legacy x86 BIOS, it is a reasonable expectation on UEFI systems with Secure Boot. Limine provides a way to modify its own EFI executable to bake in the BLAKE2B checksum of the config file itself. The EFI executable can then get signed with a key added to the firmware's keychain. This prevents modifications to the config file (and in turn the checksums contained there) from going unnoticed.
Well tough luck. It is $year_following_2012 now and most PCs are equipped with UEFI and simply won't boot without a FAT EFI system partition
anyways. It is not unreasonable to share the EFI system partition with the OS's /boot and store kernels and initramfses there.