Well I'll give my opinion when you're able to achieve that, considering it doesn't remove the benefit of the eInk.
I think side lights/leds would be more useful and effective.
I sincerely don't know why no one thought of doing something similar to the old gameboy lights (with some modifications ofc).
It would be easy to do and it would light all the screen I think.
Or maybe that's just a silly idea
But who knows.