Lol in all seriousness, mysterio coming back can go 1 of 2 ways. He can be like Jericho and put over stars and engage at the mid to sometimes upper card. Or, he becomes heel, for once, and battles at the mid card putting over guys like kalisto, Cesaro, Ziggler, etc.Nice storyline lol
The most "creative" thing would be for him to become heel and attack kalisto.
Otherwise, he goes back into a Jericho-like mode and fights at random and in gay matched. Otherwise he's useless