But, it does raise the question of how many other callers expect the bios to not mess with the segment limits. (Though, to be honest, the only goal I have with coreboot native seavgabios is support for grub, lilo, syslinux, and maybe ntldr.)
Yes, it should be good enough for bootloaders.
Emulating attributes would be great so you can actually navigate bootloader menus.
And we don't have a cursor I've noticed meanwhile. That would be very helpful for editing your linux cmd line in the boot loader. A blinking cursor is probably a bit unrealistic (need timer interrupt etc), but emulating a block cursor should be possible I think.