Von Strucker is a major Hydra leader, the evil organization of Nazi mad scientists led by the Red Skull in Captain America: The First Avenger, so you can easily see the appeal of using the villain to help connect the Marvel movie-verse even further. And with Hydra's love of evil technology, it's also quite easy to envision how the evil robot Ultron could be created, whether they do it on their own or repurpose some tech of Tony Stark's — although now that Michael Douglass has been cast as Hank Pym in Ant-Man, it's technically possible he will be the one to create Ultron in the movies, just as the character did in the comics.
As for Kreutschmann, his less-than-cheery demeanor and German accent should serve Von Strucker well. He's already played a Nazi in Valkyrie, and he's certainly done a great job at playing the not-at-all heroic or particularly sane Van Helsing in NBC's crazy-ass Dracula series, so I imagine this is another bit of casting Marvel just nailed.
One more thought: Now that Hydra's seemingly definitely involved in Age of Ultron, I think we can say that they're going to be the ones ultimately responsible for creating Ultron. Pym or Stark could create a benign AI of some sort, but chances are Hydra's going to get its hands on it and then turn it into the genocidal 'bot the Avengers know and fear. Which is fine, but one of Ultron's most interesting aspects is that he was created by one of the actual Avengers — it gives his character a pathos that very few other of their villains have. It'd be a shame to lose that in the movie, I think.
[Via The Warp]