Noah Hawley, the creator of FX's Fargo (2014) and Legion (2017), announced at SDCC's Legion panel that he is currently developing a Doctor Doom movie for Fox. Doctor Doom is a classic villain in Marvel comics, and while he is traditionally pitted against the Fantastic Four, he has also faced off with plenty of other Marvel heroes, including the Avengers. In previous incarnations of the Fantastic Four in film, he has been portrayed by Julian McMahon in the 2005 Fantastic Four and 2007 Fantastic Four: Rise of the Silver Surfer and by Toby Kebbell in the 2015 Fant4stic Four reboot. It remains to be seen whether or not the Fantastic Four will appear in the upcoming Doctor Doom film, which could easily serve as a prequel, sequel, or another reboot to the Fantastic Four franchise.
Doctor Doom is from the fictional Eastern European country of Latveria. His parents were a Romani witch and healer. His mother was killed when Doom was young, and his father died fleeing a vengeful Baron. His parents' deaths propelled Doom to combine technology and magic in order to become powerful enough to protect the Romani people in Latveria. He would later study in the United States (where he would meet Reed Richards of the Fantastic Four) and become seriously disfigured after a technological experiment exploded. As a result, Doom wears his signature mask and hood.
Depending on when the story of the Doctor Doom film takes place, the facial features of the actor in question may not matter, as they might be covered by prosthetics or a mask. Similarly, the age of the character could vary depending on the story being told. Because of this, potential actors for this project have a wide array of experiences and strengths that they can offer to the part.
If there was a frontrunner to play Doctor Doom, it would have to be Dan Stevens. Stevens plays David Haller, the lead in Hawley's immensely popular and critically acclaimed Legion. David is a complex and dynamic character who may or may not suffer from a severe mental illness. The fast-paced and quirky episodes have given Stevens the opportunity to show off his impressive dramatic and comedic range (as well as dancing, singing, banjo-playing, and accents). Additionally, Stevens' work on Downton Abbey and the blockbuster Beauty and the Beast (as the largely CGI Beast) have shown that he is leading man material. He has the acting ability, he has the mass appeal, and he's worked closely with director Noah Hawley previously.
Hawley has been known to work with the same actors in multiple capacities, using actors from Fargo in Legion (including actress Rachel Keller, actress Jean Smart, and actor Mackenzie Gray), and so it wouldn't be surprising if he picked up Stevens from Legion to play the leading role in the Doctor Doom project. In fact, Stevens is apparently already tied to the Doctor Doom project, although his role remains to be seen.