Just FYI, the native graphics work for the chromebooks works fine. But it was a long hard road to get there -- it basically took 18 months of hard off-again, on-again work.
Further, in our case, we set up the max res and bpp and use that. No modes. No text mode. No interrupts. We pass the details in the tables and the payload is expected to work it out. The kernel works it out by seeing that graphics hardware is initialized and using what it finds.
We had no desire to support text mode or int10 or any 1981-era services. Our goal was to provide a canvas in which depth charge and/or the X server could paint graphics.
So our use case is more limited than yours. I would argue that you should try to get around the need for text mode and INT10, but that's just me, since the goal of coreboot from the start was to get rid of INTxx; as wonderful as things like seabios are, they are not what we intended to have when we started the project.
In short, native graphics is nowhere near complete if your goal is a full text mode, INT10 supporting, standard PC world.
ron