So, if I decide to revive my "Alternate History of Animated Films" project, here's what I think I'll do.
For starters, like how Disney films started out distributed by RKO Radio pictures before Disney became its own company, I think I'll have the other studios like Fleischer and Walter Lantz Productions become their own individual studios as well. Hell, since Warner Brothers animation was originally called Leon Schlesinger Productions, maybe it'll continue to be called that ITTL.
Disney
Since the war didn't affect them as much ITTL, Pinocchio and Bambi will be bigger hits. MAYBE Fantasia will be more successful, though I don't know if it'll be enough to be updated with new segments as was originally planned, as it got mixed reviews even at the time. Dumbo as a feature will still be butterflied, since the entire reason it was made IOTL was to recoup the losses of Pinocchio and Fantasia, though it may end up being made as a Silly Symphony as was originally planned. Since there's no Disney animator's strike ITTL, animators like John Hubley, Art Babbit, and Bill Tytla will stay at the studio, and UPA will be butterflied.
Films released afterwards will consist of Alice in Wonderland, Peter Pan, The Wind in the Willows, Uncle Remus, Mickey and the Beanstalk, and Bongo. (I imagine Uncle Remus being mostly animated with a live-action framing device by the titular character, meaning it won't carry as much of the historical baggage that made OTL's Song of the South so problematic, so hopefully it will actually be allowed a home video release.) Other films I can see them making ITTL include Chanticleer, Lady and the Tramp, and Babes in Toyland (as an animated film). I also hope to maybe find a place for them to release the cancelled Hiawatha project.
Like in my original version, Walt will team up with Osamu Tezuka to produce an adaptation of Jungle Emperor Leo (or as it's better known in the west, Kimba the White Lion). Since Disney's The Jungle Book has been butterflied, hopefully that will result in Bill Peet staying, since his scuffle with Walt over that film was what made him leave IOTL, though I can also see him having a similar scuffle with Walt over Kimba. However, Walt's death will affect the studio more than IOTL; since Disney has more competition ITTL with other feature films from other studios, I can see this leading to the Disney company shutting down their feature film department to focus more on TV animation and live-action. (Which they almost did after Walt's death IOTL).
Warner Brothers
Like in my original version, WB's first feature will be John Carter of Mars, which will start out as a more straightforward adaptation directed by Bob Clampett. However, after Clampett left the studio, Chuck Jones will rework it into more or less a cartoonish parody of its source material, like how his previous short The Dover Boys was a parody of The Rover Boys. The success of this film will result in Dr. Seuss returning to the studio (since he previously wrote the Private Snafu shorts) to write screenplays for them. While his attempt at a musical fantasy The 5,000 Fingers of Dr. T will fail, his other more lighthearted projects like Horton Hears a Who and How the Grinch Stole Christmas will be more successful. Unfortunately, a falling-out with Chuck Jones will result in Seuss leaving the studio to focus on his children's books.
WB's first post-Seuss film will be The Jungle Book, which will adapt Mowgli's Brothers, Kaa's Hunting, and Tiger, Tiger! into a single feature. Richard Williams will join the studio after that, and the films afterward will consist of Dr. Dolittle, Willy Wonka and the Chocolate Factory, Nasrudin (which The Thief and the Cobbler started out as IOTL), The Lion, The Witch, and the Wardrobe, and Little Nemo: Adventures in Slumberland. After Steven Spielberg joins the studio, the company will produce Who Framed Roger Rabbit, and animated features after that will consist of We're Back! A Dinosaur's Story, Balto, Cats, Shrek, and Harry Potter and the Sorcerer's Stone (which will be greatly Americanized and feature the voices of Haley Joel Osment as Harry and Robin Williams as Hagrid like Spielberg planned IOTL, much to the displeasure of Rowling and all the Potter purists out there).
Fleischer
Mr. Bug Goes to Town will be more successful ITTL, and after that they'll end up producing a film adaptation of Superman. That success will lead to more DC adaptations, along with films such as Little Lulu, Casper the Friendly Ghost, and Raggedy Ann and Andy. I can also see them teaming up with Harvey Comics to produce animated TV adaptations of comic characters such as Richie Rich. And yes, like in my original version, Star Trek will be an animated Fleischer series.
After the death of Max and Dave, Ralph Bakshi will take over as the new head of the studio in the seventies, and produce his films such as Fritz the Cat and Heavy Traffic there. A lot of the series made by Filmation IOTL will probably be made there as well. As a fan of the fifties Dr. Seuss films, Bakshi will probably do film adaptations of The Lorax, The Butter Battle Book, and maybe even I Had Trouble in Getting to Solla Sollew. Then he'll end up producing a new 1989 Batman film that will reignite interest in the character. Also The Ren and Stimpy Show, Rocko's Modern Life, Ed, Edd n Eddy, and SpongeBob SquarePants will probably be Fleischer shows ITTL.
Walter Lantz
The success of Aladdin and His Lamp featuring Abbott and Costello as the two genies will inspire Lantz to focus less on shorts (especially since most of his shorts are considered mediocre today) and more on features, with the help of many former Disney staff such as Fred Moore and director Shamus Culhane. Films I see him producing ITTL include Don Quixote, The Legend of Sleepy Hollow, Animal Farm, Rudolph the Red-Nosed Reindeer, Peter Rabbit, The Musicians of Bremen, The Last Unicorn, The Adventures of Tintin (thanks to the suggestion of another user), The Last of the Really Great Whangdoodles, Willy Visits the Square World and Curious George.
Haven't figured out who will succeed him as the head of the studio after he dies, though. Brad Bird? Andreas Deja? Glen Keane? John Musker and Ron Clements?
MGM
Like IOTL, Bill Hanna and Joseph Barbera will lead a lot of the animation department, though I can also see Gene Deitch helping out as well. As well as the TV shows they're known for IOTL, features I can see them producing include Charlotte's Web, The Hobbit (I don't know if they'll do the other LotR books like in my original version, but their film will probably reignite interest in Tolkien), Where the Wild Things Are, The Trumpet of the Swan, Watership Down, The Plague Dogs, Hank the Cowdog, Tom and Jerry: The Movie, The Pagemaster, and Cats Don't Dance. Also, a lot of Cartoon Network shows like Dexter's Laboratory, Johnny Bravo, Cow and Chicken, The Powerpuff Girls, Courage the Cowardly Dog, Codename: Kids Next Door, and The Grim Adventures of Billy and Mandy may end up being produced by MGM as well.
Other
Rankin-Bass may end up producing A Charlie Brown Christmas and the other Peanuts specials, since Bill Melendez will either be at Disney or Warner Brothers at this point. Then I can see them producing the Garfield specials and MAYBE a Calvin and Hobbes special. TV shows I can see them producing include Life in Hell (an adaptation of Matt Groening's comic strip he did before making The Simpsons IOTL), and a lot of Klasky-Csupo shows like Rugrats.
I heard in the late fifties, Jay Ward actually planned his own adaptation of Winnie the Pooh as a TV show, so I can see him beating Disney to it ITTL.
I haven't figured out what Don Bluth will do ITTL. Disney shutting down will prevent him from finding many opportunities there, and I don't know if he would be interested in pitching his ideas to those other studios. My original version had him joining Fox's new animation department consisting of many former Disney staff, so maybe he could do that here as well?