Memorised my options essays for legal and got 96. That being said, I did have a thorough knowledge of the topics and would have been able to twist my master essay to fit any question. I would never have just regurgitated it word for word.
Definitely wouldn't memorise anything for the crime mini-essay, it's too broad.
It's impossible to memorise essays for modern - as cem said, you would need at least 40 essays. Some people memorised brief essay plans for possible questions, or made mind maps of syllabus points showing how they would link each topic.