Write the... ultimate Martian Manhunter story?
Let's face it, the Martian Manhunter has never exactly been known as a story engine. His main function, since days of the BWAHAHA-Justice League has been to be "the heart" of The Justice League. What that mostly entailed was being... in The Justice League.
And talking about the human condition.
Or lifting the stuff Superman or Wonder Woman aren't lifting at any given moment.
Or using his Martian vision on stuff.
That is to say, The Martian Manhunter has become to The League what the hat became post-Kennedy inauguration, a lovely piece used to accent the ensemble but wholly unnecessary to complete it.
Until Joe Kelly and one story. J'onn J'onnz, The Martian Manhunter's one weakness has always been fire, the reasoning being that all heroes need some sort of weakness for a villain to exploit i.e. Superman and Kryptonite.
So, what happens when a hero conquers his weakness and goes on to become what he is: the most powerful member of The Justice League.