Probably not much. I'm betting he'll be a quick character we see as an introduction to Batman. He won't do much other than be a badass way to re-introduce the dark knight on the big screen.

Victor Zsasz was already in Batman Begins. Just a throwaway character unfortunately.

Just depends on how they do it. The likelihood of them having any significant screen time is minimal. I mean, they'll mostly be there to flesh out the overall world and give the 'universe' more weight, rather than overtly affecting the story. Think of it like Batroc the Leaper in The Winter Soldier. That character for that scene didn't HAVE to be Batroc, but it's a cool nod to the comics and helps get the plot moving in the right direction.

I'm guessing that's how these "villians" will be as well.

Wasnt there rumours of Doomsday?

I wouldve loved to start off small though. Lex and Metallo as villains in the next movie, then Doomsday, then Brainiac, then finally Darkseid.

Maybe throw in Warworld/Mongul in there too for good mix.

Superman's strengths aren't in his abilities to be stronger than everyone else, it's his tough decision making and creativity that make him a compelling character.