Movies: why is deathstroke the main villain in the upcoming Batman movie?

Look with Ben Affleck directing, writing and staring in the upcoming solo batman film, you know its gonna be good or at least watchable. I mean since in the DC cinematic universe is using a middle aged version of batman and they showed the Jason Todd robin suit I was hoping they'd do the red hood storyline (which is one of my favorite comic book stories ever). Look I like deathstroke and he's a badass but he's more like a reliable mercenary who can outsmart and outfight some of DC universe's biggest hero's but he's never really been main villain material (except when he's fighting teenagers). Look I know their are comics where batman and deathstroke throw down but in the movie does somebody hire him or are they gonna do what they did in Arrow and have him be the leader of a band of highly trained mercenaries? Any thoughts?