My only change would be Atomic Skull (save him for the Elite film
) with Killer Croc (should he survive Suicide Squad). But here's why, although there are a huge crop of Superman villains out there I think given this is a DCEU wouldn't it be cool if some villains crossed over to other movies? This would be a different approach to what Marvel does. So this film would gave the cross pollination (Croc/Batman cameo) as well as developing a new character for a solo (Lobo) without overshadowing our main character.
I think an opening where a masked villain has robbed a bank and killed/maimed people on the run we see Superman come after him. The masked assailant makes his way onto a train, Superman catches him in the inter collecting links of the train (at this point he's demasked) he tells him to give it up but instead Croc breaks the coupling holding the carts together and the train derails. Superman in an epic sequence saves the train.
Killer Croc is then in the sewers thinking he's got away but as he scurried away he bumps into Superman who knocks him out. He takes Croc back to Arkham where Batman is sat on a rooftop, they have a little banter about Superman taking out one of the Bats villains.