@Ebri: It should technically be possible, but parsing an OPF in an ePub is a whole different kettle of fish

. And that's if KOreader's history is updated at the right time (which it might, I haven't actually checked. Trivial to tweak on KOReader's side, though, so not a huge problem).
I personally probably won't ever implement this, but I'm welcome to a patch if it's done in a remotely sensible way

.