I think you better choose blockchain technology as topic rather than only bitcoin. Blockchain will be wider topic and inside it you can talk also about altcoins which may be enough for an essay.
Hmm you're right, what topic/question specifically would you suggest I research on feature/limits/advantages of blockchain?
you can search about the bank blockchain technology and ocmpare it to the real blockchain, and see what it will be the advantage for them to run one instead of remaining with fiat