My parents used to raise rabbits when I was younger. They have the potential to be more dangerous to a keeper than a rat, but if bred properly should react by freezing up, not by getting aggressive.
I imagine the danger to the snake would stay about the same if not less (since an 18 ft burm is proportionally bigger compared to a rabbit than a BP is compared to a rat), but that's pure conjecture on my part since I've never worked with any of the larger snakes.