1,2, and 5. Sorry, too many!
1 sounds like a virtuous and interesting effort, but oh, the research necessary to make it realistic! Could you manage it in the time allowed?
2 sounds interesting because it would by its nature include us, and of course that makes us feel important! But I think aside from that aspect, it would be appealing and interesting.
5 because I love spooky mystery novels, period. But besides my personal preferences, this might be the easiest to write quickly, as little research outside the magical corridors of your own mind would be needed.
So, I'm no help at all!
But having read some snippits of your writing, I suspect you could pull any of them off - good luck!