Grub.cfg help request

[shelly16]

hello

I've been trying to write a grub.cfg that does what I want, without 
having to patch the source code but I don't think it's doable.
Can you advise ?

here is the synopsis:

if shift not pressed
try
find a luks2 partition named foobar on the sata bus
mount it (ask for the passphrase)
load mygrub.cfg from this partition
boot the default boot option
endtry
endif
display a password protected menu
- boot seabios
- boot tianocore
- grub command line

do you see something not doable by a grub.cfg ?