This idea is really simple. If you breed two rabbits together, there is a 47.5% chance of the offspring having the same fur color as one or the other of it's parents, and a 5% chance of having the fur type matching the current biome. I believe that the natural type of bunny for The Nether is the Killer Bunny!
Now, I'm not proposing that Killer Bunnies start spawning in The Nether, but if the player transports a pair of normal bunnies from the overworld into the nether, and then breeds them there, the offspring should have a 5% chance of being killers.
In other words, unless someone has already built a rabbit farm in the nether, they won't be unpleasantly surprised by this change to the game.
As for why to add it back, just because it's an old joke, doesn't make it less funny. Also, I can easily imagine players on a PvP server deliberately breeding them, nametagging them, and penning them around (or inside) their base as part of it's defense.
Once you have your first killer rabbit, you can breed it with one of the normal rabbits you brought into the nether, and the baby rabbit that results will have a 52.5% chance of being another killer rabbit.
And if you breed two killer rabbits in the nether, the offspring has a 100% chance of being another killer rabbit.
This is the exact same mechanic used for biome specific fur types. I don't see any reason why the percentages should be changed.