How about Elizabeth Debicki for the role of Jessica? She's only 27 y.o., but I think you can put her anywhere between 25 to 40.
I still have her as my choice for Princess Irulan - and Irulan is described as being tall which works in Debicki's favour.
And I still stand with my suggestion of Sylvia Hoeks as Jessica. I'll be thrilled if the announcement comes true!
Looking forward to who they cast as Chani too. I still like the idea of Brianna Hildebrand, but I'll be happy as long as the chosen actress looks the part. Hailee Steinfeld too, perhaps?!
Also read some great suggestions recently with Robbie Coltrane (didn't know he was in remission actually) playing the Baron Harkonnen and Sigourney Weaver as the Reverend Mother Gaius Helen Mohiam. I can definitely see it with the both of them. While Vincent D'onofrio and John Goodman are favourites for the part of the Baron, I see them as being too physically intimidating. That's not how I think of the character, IMHO. I still like the idea of Albert Finney due to his voice though. Check out his portrayal of Winston Churchill in The Gathering Storm. Something like that.
I'm also open to the idea of Doctor Yueh being an Asian actor because uh, the name - and of course, Legendary too, I suppose. You could pick anybody really - Chin Han? Donnie Yen? Chow Yun Fat or Ken Watanabe?
Also, how about Jeremy Irons as Thufir Hawat?
I also like the idea of Toby Jones as Piter. I did think of him a while back too. Also, how about Andy Serkis too, perhaps?
Oh, and after some consideration, I can definitely see Timothée Chalamet as Paul. Looking forward to further announcements...