Only one of this pair has had their morning coffee...

I once had an idea where they both died, but were given a second chance as...
Ghost Cops. RIPD style. *Their eye color would stay the same for the reader anyway*
Different appearance to living animals, different voices, etc.
Different genders, etc. Maybe spiced up so they'd have the tastes that fit the body.
Like if Judy was in the form of a predator... She'd have a craving for meat.

Also not gonna lie, after reading the original comic again recently. I could actual see there being a continuation comic of sorts. Not necessarily a big one, but like an epilogue one.
Like Nick's election for mayor succeeding, but after he gets elected..
He starts having dreams, strong and vivid.
At first they seem just happy memories he had with judy, but then..
They become something more lucid, start to influence his waking days in good ways.
Maybe Judy speaks to him from the afterlife through his dreams, so that they BOTH can make zootopia a better place despite her being gone.
Could even have there be a hint that she really was communicating through his dream, like she tells him something only she knew.