It is not "just" ideological. It has to do with the fact that UEFI (sadly) is bug infested, also due to the fact that even the reference implementation is way too large. It is full of nonsense also (vendors love to put in animations of spinning fans, "3D" setup menus and other crap). It has to do with performance. It has to do with royalties / licenses to be paid for this mess. And last but not least it has to do with security and privacy. A firmware that is so huge like the Linux kernel without drivers, wow, that leaves a lot of open surface for attacks / security holes, general bugs or intentional backdoors.
So Coreboot would probably be not the worst choice. They can add some Seabios payload in case somebody needs to install Windows on it (which afaik still does some BIOS calls).
Stop TCPA, stupid software patents and corrupt politicians!