i dident play 'Left in nowhere' map yet (maybe i will)
but i have an idea:
1: You start in a jail with a police guarding you
2: a zombies attack the police and the door of the jail will crashed
3: then you move for a while and found a weapon (melle weapon)
4: fight with zombies and each time you go you find another weapon
5: you go to a small lab with death guys (images) with Electricity you must turn off the power first
6: at the end make a plane that you must go to another and the 2nd towen will be part 2 and this is part 1

add your own ideas and i think that is something hard.
sorry for my english if any wrong becaus i am not english but i know
ThE eNd.