Oh look a character with less story relevance than the Paradox Brothers. NEXT!
But seriously though. Duke would be even worse than regular Marik. We already have a gambling duelist, and even in season 4 Duke doesn't really do anything. He's just kinda there. He doesn't have a deck profile, except Orghov and Dice Rolls... basically less-interesting Joey.
To continue, Bonz at least has story relevance. Him and his gang, under Bandit Keith, kidnap Joey and take him to the cave which eventually leads them to the Paradox Brothers and their final star chips. In his 2nd duel in Battle City, his loss illustrates Bakura's power, and gives us the most terrifying vision of losing a shadow game in DM.
Idk about the anime, but for manga, what the anime based on, this Duke Devlin is far more relevant than stupis Bonz. He has his own game and was a big part of Yugi character development. A whole volume of the series is devoted to him.
Seeing as I haven't read the manga, and the anime is what's relevant, mind telling me how exactly he develops Yugi? Because in the anime, he has Dungeon Dice Monsters, but as for relevance to the story? He hangs around in seasons 2-4, but is about as useless as Tristan, and doesn't even get a robot monkey arc. Heck, Pegasus does more for the story in GX than Duke does in all of DM.
It's a bit different in the manga, he took Yugi millennium puzzle and the once who played against him was yugi muto. Apparently, his family had a dispute with yugi's granpa over who would own the puzzle.
Duke is far more prevalent in the anime, and games than Bonz. I would also prefer titan. Archfiends are great, and we already have pumpkin princess. I understand the pumpkin Halloween cliche they want to portray, but please put more thought into this Konami.