I mean, (almost) anything is possible on a jailbroken device, you just have to be willing to get your hands dirty

.
But I kinda agree with @Quoth there, nightmode on eInk is an aberration, even if the implementation on the Oasis 2/3 is the *least terrible* one I've seen on eInk.
(i.e., my only interest in it is the technical aspect of the implementation).