But it's not a firmware issue, the Kindle can do non-flashing updates fine and does them all the time with menus.
It's the actually book reader program that adds the image in to the buffer then calls something to update the screen. (Or so I believe)
If someone was willing to reverse engineer the Kindle book reader program then maybe release a patch or something... I'm not sure about the legality of a patch though.
I suppose it's possible if you make the user decompile and edit the file themselves...