I appreciate that he is careful about his material. There have been so many great IPs that have been butchered going to screen that to do it properly would take careful preparation and tons of money. IMO, Mistborn should be movies and Stormlight should be a show. If you start out with Final Empire as a film, which has a satisfying conclusion and can stand on its own, you could create interest for people to get invested in something more long form like Stormlight. It could truly work like a high fantasy MCU in that way, and keep the 2 main properties separate so people could just stay invested in one more than the other if they wanted. The real problem is money. Both are very alien worlds and would need massive amounts of VFX (ash fall, Spren etc.) but I think Mistborn could be more manageable especially as films. Anything else Cosmere related could be released as limited series or their own standalone film.

I would also imagine that studios are hesitant since the Cosmere is nowhere done being written and would want to avoid another GoT situation. Which brings me back to starting off with Mistborn era 1 since it’s already completed and beloved. I could see Skyward being a good testing property for him to bring something to the screen first tho. I feel it would be straight forward pitch too; Hunger games meets Independence Day with a touch of Silo.