In theory, though, the even better option would be for linux to be coreboot-aware enough to be able to write into the firmware modifications from userspace to set this stuff, so you can tweak your voltages / cpufreq / ram timings from a live system. I figure the only real safeguard you'd want like that is if you have 3 failed boots in a row or something it resets to the defaults so it can cleanly boot.
I thought that was the general idea? You already can change a fair amount of things from userland, like overclocking GPUs. Editing UEFI variables is another example of interaction between the firmware and the OS (adding boot entries and changing entry order is not so different from changing any other firmware settings). So it sounds doable.