The very first thing Mr Sandberg should do is bring in Alex Ross to be the project's creative consultant, and perhaps also a producer. He is one of only a few contemporary comic book talents who really "gets" the World's Mightiest Mortal. Just as Johnson's manager, Dany Garcia, is working hard to make sure the Black Adam character is perfect, it should be Alex Ross' privilege to do the same for the Captain Marvel character. The film should use Ross' version of Captain Marvel's uniform, but it should not be skintight spandex or muscle enhancing rubber. The model of Tom Tyler's costume from the serial should be used, where the top is more of a jacket, and the pants, while snug, are not actual tights. Need I say, no hoodie cape, please. In addition, I would suggest artist Jerry Ordway be brought in to assist in creating the design for Fawcett City, with its unique blend of Art Deco elegance with Norman Rockwell Americana. The definitive film needs to have a good balance of fun and humor with action-adventure and drama and pathos. I would like to see the film use tilted ("Dutch") camera angles, much like celebrated film maker Orson Welles pioneered, to give it a unique look.
The film itself needs to stay away from the horribly failed Curse of Shazam reboot. The movie should have its foundation on the works of Alex Ross, specifically Justice and Shazam: Power of Hope and the recent, and very successful Thuderworld Adventures by Grant Morrison and Cameron Stewart, as well as lifting the Billy Batson-Uncle Dudley relationship from Roy and Dann Thomas' Shazam The New Beginning. The primary influence and tone should come from the Fawcett comics of the 1940s. When Otto Binder and C.C. Beck hit their stride, they produced some of the greatest superhero adventures of all time. Previous attempts at developing the movie over the past decade seemed married to the "Big with superpowers" concept. This concept keeps the character trapped in a goofy, juvenile stereotype. Cap should not act like a 12 year old. He has the wisdom of Solomon, which should make him more mature and less headstrong than Billy. The movie could use such a Big concept in a subtle way, but to go over the top, as most recent comic book stories featuring Captain Marvel have, would be a critical mistake. I encourage Mr Sandberg to bring in Henry Danger creator/producer/writer Dan Schneider to tweak and polish Henry Gayden's script. Schneider would be a natural to capture the whimsy and humor of the original Fawcett comics, and could give the tone of the script the youthful energy that helped make Spider-Man: Homecoming such a hit.
As in the Fawcett comics, Billy should be the star of the movie. Its his adventures we follow. Yet there still must be a lot of screen time and action sequences for Captain Marvel. I speculate the creators of Captain Marvel had the Old Testament book of Tobit in mind as a muse. In it, the mighty archangel Saint Raphael takes the form of a teen, Azariah, while among mortals. I suggest all Captain Marvel fans read this book. If you don't have a Bible with the deuterocanonical books, here is a link for Tobit. Mary and Freddy should be supporting characters the film, but they should not get their powers until the sequels. Needless to say I do not want to see the three new52 kids, Darla, Pedro and Eugene, cluttering up the film. And despite some fans clamoring for it, I do not want to see Superman in anyway in this film. This movie should stand on its own, much like Wonder Woman did. If there must be a cameo with an established DCEU character, Gal Gadot's Wonder Woman would be the most preferable and make the most sense. A completely outside of the box choice, Margot Robbie's Harley Quinn, would be as unique as the chemistry Harley and Billy share in the Injustice line of comic books. With Black Adam out of the picture, it may be a good idea to introduce Ibac for a central action sequence. In the Golden Age, it was Ibac, not Black Adam, who was Captain Marvel's evil counterpart.
The elephant in the living room needs to be addressed. Captain Marvel's name. I am vehemently against the idea of renaming Captain Marvel with the wizard's name, Shazam. In a perfect world, the film makers will just call him Captain Marvel, as it should be, and let the chips fall where they may. But I fear some backdoor politics may cause that name to be off limits. If that's the case, I would advocate for Captain Marvel to be nameless in the movie, just as the name Wonder Woman has never been spoken in either of the two movies featuring her. The end credits should credit the actor playing him as "World's Mightiest Mortal", and leave it at that. In fact, "World's Mightiest Mortal" should be the title of the movie. Another idea is to borrow a gag from Spider-Man Homecoming. In the final scene, a crowd of people surround Captain Marvel. For the first time, they ask "who are you?" He replies, "Captain Ma--" cut to black, end of movie.
Perhaps the most infamous Captain Marvel fan was/is Elvis Presley. The definitive Captain Marvel movie must have an Elvis soundtrack. Mr Sandberg has stated Guardians of the Galaxy is his inspiration for superhero movies. It had a prominent soundtrack, and for the Captain Marvel movie to follow suit, Elvis performances need to be represented, if not dominate. "If I Can Dream" would be a perfect theme song. Many of his under appreciated 60s tracks would fit the film perfectly, like "Long Legged Girl" for Beautia, "What A Wonderful Life" for Billy, "That's Someone You'll Never Forget" for Billy's crush on Beautia, "Kiss Me Quick" for Beautia's longing for Captain Marvel, etc. Perhaps Duane Eddy's hit instrumental "Shazam" could be incorporated into the score.
Captain Marvel - Lou Ferrigno Jr
Alternate picks: Derek Theler, Wes Bentley, or Daniel Cudmore.
Billy Batson - Colin Critchley.
Shazam - Tim Allen
Alternate picks: Michael Keaton, James Caan, F Murray Abraham, James Woods, or Max von Sydow.
Dr Sivana - Jackie Earle Haley.
Alternate pick: Michael D Cohen
Beautia - Virginia Gardner.
This bombshell-in-the-making would be perfect for the World's Sexiest Woman.
Alternate picks: Tori Anderson, Suki Waterhouse, Haley Bennett, Genevieve Morton, or Carla Sonre.
Uncle Dudley - his royal majesty Micky Dolenz .
Mary Bromfield/Batson - Jade Pettyjohn.
Alternate choices: Breanna Yde, Reagan Strange, or Saylor Bell.
Ibac - Brett Azar
Sterling Morris - Jon Voight.
Alternate pick: Dan Aykroyd.
Mr Tawny - Jim Belushi.
Freddy Freeman - Levi Miller.
A talented young actor who can bring the darker, more serious counterpart to Billy to life on the silver screen.
Freddy's Grandpa - Alan Alda.
Nick and Nora Bromfield - Jim Caviezel and Kristy Swanson