The Bulats

Bringing the Bulats into the show would give The Punisher a contemporary feel. And that is because the Bulats (both the father and the son) had an issue against the Muslims. Of course, their background should be changed, from the Bosnian War to anywhere in the Middle East.

But the principle would be the same. The Romanian mercenaries arrive in New York and, after the Defenders have cleared the way of other big baddies, establish themselves as the new bosses. Whether it would be prostitution rings, whether it would be anything else, this would set them up on a collision course with Frank Castle.

But I guess it would be better if The Slavers were adapted in full. I believe that Frank would have even more reasons to hunt them down with extreme prejudice if they were the leaders of forced prostitution rings.

And it would be way better than what we saw in Punisher: War Zone, starring Ray Stevenson.