Use unified kernel images by default for new releases. This can allow for the local installation to sign the kernel and the initrd, so the boot chain can be verified until after the uefi. Currently, the initrd can be modified by attackers, so even if the / partition is encrypted, the systems data can be read on the next boot. If the kernel image, which includes the command line, and the initrd, is signed then it is harder to comprimise the system. The system can still be comprimised if the uefi is modified.
If this was used, then the kernel could no longer be signed in the package by the fedora infrastructure. To still support secure boot, the kernel image would have to be signed be key stored on disk on every update. If the disk is encrypted, the private key can still be protected from attackers. On installation, or update for existing installs, a public/private keypair would be generated, and trusted by the shim.
This has a few problems, if the root user is hacked, then the kernel can be tampered with. But this is not a very big problem because if the root user is hacked, then for example systemd can be changed, secure boot will not protect you. It will also mean that if the user want to modify the kernel command line or initrd, they have to regenerate the entire kernel image. This can also break some users install, if they use a non-default boot process, or have a buggy uefi implementation. For non-uefi architectures, this change could be ignored.