no, a mok is just adding an unprotected UEFI variable. It's not the same as adding your key which can say disallow running payloads signed by Microsoft key.
On one of my systems disabling secure boot also disables other aspects of the BIOS. I forget what, maybe use of the Intel graphics on the chip? It was severe enough I spent an hour figuring out how to make secure boot work instead.
Software can still modify the bootloader. Secure Boot does not protect against that. It just will complain on the next boot .... unless the replacement bootloader has been signed with the MS signature, the BIOS manufacturer signature, the OEM signature, or a bazillion other signatures.
Even if you were to completely replace all of the signatures with your own, you are going to have to trust some of the MS/manufacturer ones (unless you replace all the manufacturer-signed firmware modules with your own).
>unless you replace all the manufacturer-signed firmware modules with your own
... of which there might not be any. Eg none of my half-dozen SB-using systems (desktops and laptops) have anything in the ESP other than the booloader and UKIs I put there, and boot with my own keys just fine.
I think this is not general enough. What would be needed is the Microsoft secure boot private key so we can just sign EFI binaries and have them work everywhere without mucking around in the bios setup.
Afaiu, this key is specific to certain generations of Intel CPUs.
There seems to be a bit of a precedence with the AACS DVD encryption keys that got leaked (https://en.m.wikipedia.org/wiki/AACS_encryption_key_controve...), the suppression of that key. Seems to have failed, it was widely copied, and you can even find a copy of it on my link to Wikipedia.
"Your honor, I wasn't copying that movie. You see, I applied a mathematical formula to the .zip file, and it just happened to produce the movie as output. Coincidence!"
(That's not to say the key is copyrightable, it's not. I think the relevant law would be the DMCA anti-circumvention provision.)
"I didn't distribute the movie, just a file that XOR'd every byte with 255!"
Technical people tend to see the law as a technical thing, where technical arguments will win. Courts are generally unamused, since every judge has years of experience with defendants who think that they've discovered one simple trick.