I'm sure this is a naive take, but why is it not possible to enter a new key into the BIOS (dating myself, I know it's EFI) by hand?
You can keep the Microsoft keys in there if you want to dual boot Windows, you just need to re-sign the keys themselves with your own PK.
I'd argue that it only helps check a tick box on corporate security manifest, as it indicates the kernel being booted, is not tampered with.