Thanks for the advice.
This a device for playing, I intend to break it

I have a backup stock SD card that works perfectly.
So I have no fear
So if I do that, what will be the problem?
I have heavily modified the rcS script and inittab so far (I am quite fluent in Linux) and so far it's working great.
The last two lines of rcS are hindenburg (graphical system? Touch system?) and nickel (desktop + reader?).
So my idea was simply to insert koreader between the two. So when I quit koreader, it launches nickel.
What can you tell me about that?
How would you do that?