Let the mastermind villain hire some muscle. Mercs from around the world. The best of the best.
1) Bane
Big Brazillian guy, talented merc and bounty hunter, raised on south american geurilla warfare, a little accent and utterly badass. Wears standard Paramilitary uniform type stuff. Face is more Ghost Recon than spandex mask. For the film's climax, let him take some drugged adrenaline he acquires for a pumped up fight against the Bat. He doesn't have to carry the show or be a huge part, but having him try to doublecross the mastermind in the end would be a nice touch... especially if he's slick and successful.
2) Deadshot
Pretty easy. A Gentleman sniper, English sort, very much Gotham Knight, give him fine clothing (in his comic costume colors) accented by slick briefcases with gloriously disturbing looking customized weapons. Add to this a infrared/telescopic monocular, and you have deadshot, but realistic and easily used for film.
3) Lady Shiva
Michelle Yeoh, please. Unrelenting, unforgiving, unremoseful and utterly untouchable in hand to hand combat. Former League of Shadows. Keep her pretty simple in her quest for a combatant worthy, but stay away from that stupid 'giving them a chance and getting killed for it' trope.
4) Ventriloquist
This would be the most fun to update. Instead of trying to emulate the cartoon, let Ventriloquist be a skilled hitman, one that seems entirely mute. Couple this with his 'Scarface' doll which actually does do the talking, and can actually be pretty comical, and you've got a pretty interesting character, that doesn't demand a lot of screen time and can have a really REALLY cool death scene.
Get these four together and you've got four really cool fight scenes, with four classic batman villains, without having to delve too deep into their psyches or go out of your way to explain something inhuman because everything they do is completely normal.