If you wanted to try that, the best place to do it would be the UEFI setup code in the kernel under arch/x86/boot/compressed/eboot.c - that way you can do it independent of bootloader. Grub's able to read files anyway since it's using the firmware calls to do that.

The power management thing isn't about the SSD itself, it's about ensuring that the controller is programmed correctly so that the entire CPU package can enter deep sleep states. Modern systems should idle at around 4W at most, so small amounts make abig difference here.