My map is all jungle (filled in to almost the ceiling of the map), and there are plenty of ocelots if that helps (maybe replacing every other ocelot with an evil rabbit and every other evil rabbit with a vex or something? Regular rabbits would be cool, too, so that players can hear rabbits but not know which type it is, but I don't think they spawn in jungles.
Oh. hmm... well I tried all the new entity data values for pigs: minecraft:pig, 90, and even 5A which I didn't think was going to work anyway, but none of them worked. I do want it to work in 1.12, actually. Still confused :s
Why not experiment a bit with mob spawners? There's a bit of a bug with custom mob spawners (though I haven't tried this in 1.12.2 yet) but if you set a mob spawner using an egg then it will retain the mob.You could even get yourself a mob spawner which has specific customized spawn rates, then set the mob with a spawnegg and leave it at that.