(Post continues from above... again, I remind people that I have many spoilers in this; don't read it if you don't want advance knowledge of some events of the novels)
Technically, one of those already happened, since Virginia Madsen didn't have many scenes in the Lynch movie, and Irulan was trained by the Bene Gesserit (although she never went through the Water of Life ritual to become a Reverend Mother).
Whatever they do, just please don't make them look like witches who are either bald or have straggly mop hair and funny hats...
It's kind of hard to imagine anyone else in that role.

The one in the miniseries was pretty forgettable.
One of my friends in college really liked the Lynch version of Piter, and practiced all the hand gestures he used when speaking to the Baron and his nephews.
No, I don't think so.
We need to remember that Irulan's role in the miniseries was expanded beyond what was in the novel, and played by an actress who was able to make her acceptable as a warm, sympathetic person caught between politics, conspiracies, and trying to find some kind of place for herself not only in the Atreides Imperium, but also as a member of the family.
The novel version of Irulan is a very cold, unlikable person in the first two books. In fact, Frank Herbert wrote a scene for
Dune Messiah, in which he intended to kill her off - as one more victim of the Fremen mob intent on putting down the conspiracy against Paul. In this original version, Irulan was visiting Mohiam in prison and was caught in the wrong place at the wrong time, and was killed. I'm glad he changed his mind, since otherwise we wouldn't have had Julie Cox's excellent interpretation of her in the miniseries.
The one really stupid blunder made in the miniseries in casting the Corrino family was using Susan Sarandon as Wensicia. Irulan is the oldest, so her younger sister shouldn't be played by an actress a generation older. That was ridiculous, and Sarandon didn't seem to actually understand that Wensicia was a hard, bitter, driven woman, and not someone who indulged in hammy over-the-top showing off. The goofy hair accessories didn't help, either.
I don't think Irulan could possibly replace Margot Fenring. For one thing, it would require her to be on two planets at the same time (Margot left a message for Jessica on the underside of one of the leaves in the conservatory), and later on, Margot was assigned by the Bene Gesserit to seduce Feyd-Rautha and conceive a girl. I can't imagine Irulan pulling that off, and if she'd had a child, that would have called into question whether or not she would still be fit to be Paul's consort.
She has a very noticeable role - her writings are what introduce every new chapter. She reveals not only objective history in those, but also some personal details.
And I think that's why, in
Paul of Dune, KJA/BH deliberately retconned that. They didn't want Frank Herbert to speak through anyone. They deliberately went out of their way to say that everything she wrote in Dune was a lie that Paul told her to write, that
Dune itself (the original novel that all the rest of this is based on) was nothing more than in-universe propaganda. They retconned a bunch more stuff in
Winds of Dune (the Bronso of Ix nonsense), and thank goodness they didn't get around to wrecking
Children of Dune.
No. Just
NO. There is nothing they wrote about Irulan that doesn't show her as a pliant puppet who writes propaganda at Paul's orders.
If those two have any say at all in what goes into this movie or how it's written, it will emphasize their own drivel, retcon as much of what Frank Herbert wrote as they can get away with (really, Paul was not born on Kaitain, nor did he run away with Bronso of Ix and join the damn circus), and I predict that Norma Fucking Cenva, the millennia-old deus-ex-machina character who shows up in Sandworms of Dune to save everything will turn up somehow.
The martial arts aspect is something I don't have much problem with. After all, that's a part of how some Bene Gesserit are trained.
Rubber stillsuits were a problem. They were used in the movie because they "looked neat" - not because they were actually practical. A lot of the actors really suffered while wearing them, and in one of the scenes where Rabban is climbing up one of the dunes, the actor was
thisclose to passing out (this is related in Ed Naha's behind the scenes book
The Making of Dune).
And the special way the Fremen were supposed to breathe, to conserve the body's moisture... absolutely did not work in the Lynch version. The actors basically abandoned it soon after the scene where Liet-Kynes explains how to use them (which was the reverse of how it was explained in the novel).
The miniseries did a much better job of designing the stillsuits, both in aesthetics and function.
Any use of lasguns on Arrakis was frowned on, because when you get a lasgun intersecting with a shield, everything goes BOOM! in a pretty big and destructive way. That's why there's such an emphasis on knife combat and martial arts. There's much less chance of attracting a worm or causing an explosion.
I've just skimmed a few chapters of
Heretics of Dune. Some chapter quotes are from Leto's journals (before his death, obviously), but most are from various Bene Gesserit sources. I don't have
Chapterhouse: Dune handy, but I would think that it would be similar. Irulan is no longer the primary narrator, and that makes sense as she's been dead for thousands of years at this point and nobody saw fit to re-create her in ghola form.
Yes, you should read all of Frank Herbert's Dune novels before the rest of it (the better to understand that Frank Herbert's novels are a gourmet feast for the mind while nuDune is just slop).
I also recommend at least skimming the
Dune Encyclopedia (particularly the articles about the history of the Imperium, the Spacing Guild, the Fremen, and the Butlerian Jihad). The Encyclopedia had Frank Herbert's approval - which makes it canon as far as I'm concerned, with the exception of whatever details Frank Herbert himself retconned in Heretics and Chapterhouse (as he told Dr. McNelly he might do).
There is nothing irrational in my dislike for the BH/KJA garbage. They are simplistic stories that spit on the source material (not respectfully like a Fremen, but contemptuously, to erase the rich legacy FH created in favor of their own stuff).
One part of science fiction is
science... which is noticeably lacking in some pretty basic ways in nuDune. For instance, I find it hard to respect authors who don't realize that when you're fighting a space war with STL ships, relativity matters. Instead, they treat an hour on a ship as the same as an hour on Giedi Prime. Everything happens at the same rate everywhere, when it shouldn't.
And it appears also to have slipped their minds that space wars are normally fought in three dimensions, not two.
But... but Kevin J. Anderson dictates perfect prose while climbing up and down mountains, and any mistakes are his secretary's fault! He said so!
Apparently that's why his novels are so repetitious, like the reader can't be trusted to remember something from a few pages ago. Apparently he can't remember what he dictated a few pages ago, either.
Yep. Years before leaving Caladan for Arrakis... where it's explicitly stated that at age 15, Paul has never been off Caladan before.
But nooOOOooo... KJA/BH just couldn't let that stand. They not only had Paul born on Kaitain (and kidnapped), but 12 years later they had him stow away on a friggin' spaceship and join the circus!
At this point, do you honestly think there were any notes beyond the unfinished manuscript for "Dune 7"?
I don't. Or at least if there were, they were nowhere near as extensive as claimed, and it's obvious that KJA/BH just ignored them anyway in favor of their killer robot and Norma Cenva, Superwoman! garbage.
No, they really don't. Frank left off with Marty and Daniel in human guise, talking about gholas and Face Dancers.
KJA/BH retconned this into Marty and Daniel being Erasmus and Omnius in disguise... which is just so damned cartoonish and an obvious declaration that Hunters/Sandworms are sequels not to Frank Herbert's version of the Dune sage, but to their own version. So 15,000 years later, characters from the Butlerian Jihad turn up (apparently they've just been sitting around twiddling their robotic thumbs for all those millennia until the Honored Matres found them in the Scattering and Norma hasn't done anything about them because she's mutated to the point that she barely remembers being human anymore and only occasionally recalls such things... fortunately in time to save everyone at the end).
Yep. Ghola-Leto gets a second chance to grow up human, and what does he do? Turns himself into a worm. Again. At least ghola-Paul and ghola-Chani are together... on a dead planet.
I don't actually remember what happened to ghola-Jessica. She was so boring, I don't even care.
And one of the creepiest things about that whole thing... in the no-ship, when Duncan's feeling lonely and discovers he's still got a strand of Murbella's hair and remembers what great sex they had... should he have a ghola made of her, so they can have great sex again? It's creepy enough if the ghola were created as an adult, but they're born as human infants are born, and Duncan would have to wait for Murbella to grow up and remember her former self and realize how skilled she is at Honored Matre and Bene Gesserit stuff, including all that great sex with Duncan...