I often ask myself, how would the game look through the eyes of the character I use, in a MOBA is the same, think of how you look at it, and how much it changes when you are on that place, if you want to make it related to the Esports then you should think which are on the competitive scene and find one that you thinks work the best to your aim.
The underdog theme is always nice, another spin is looking at it through the viewpoint of someone who is already at the top but lost the thrill, similar as to how Saitama on One Punch Man doesnt feel any emotion on his fights because they end in one punch, imagine being the best and losing the thrill that made you get there? What are you supposed to do?
A dark fantasy is always neat, but you got to think well what exactly is your aim, what could you be losing? what could they be betting? is the reward worthy of trying?