It sounds like a very bad idea. For much less money you could get a
real device that has:
a 10x better screen (I would say 1000% better
)
with frontlight
and touchscreen
a PMIC and battery
linux kernel support for all those things.
it is already supported in KOReader
Buuut if it is just for the fun and you want to waste a little money and much time, you'll need a bunch of things missing on your steps, including
- write a new device abstraction for your particular device (sdl works on computers with a desktop environment or on EGL surfaces, both work on the pi, but not your thing)
- write the output module that interfaces with your kernel driver)
- create some sort of input, write the input module
And a bunch of other things.
If you want to play with a Pi it is better to skip those sh***y eink screens and get yourself a 7" touchscreen display, where both input and output should work almost out of the box with the SDL version of KOReader (arm64, if possible) even without Wayland/X