“Magical Mystery Cure” shows us how difficult it would be for the Mane Six to do each others’ jobs. Fluttershy, a timid pony with stage fright, is terrible at entertaining the citizens. Pinkie Pie, who isn’t used to hard, serious work, finds herself incapable of managing the apple farm. Applejack, a mare without an eye for detail or any design skills, can only create unattractive outfits for the boutique. Rainbow Dash, who isn’t a gentle soul like Fluttershy, finds it difficult to handle all of the critters. Rarity, a unicorn whose more into fashion, finds weather duty nearly impossible. The entire conflict of the episode comes from their inability to perform each others’ tasks satisfactorily. As a result, Twilight Sparkle is desperate to switch back their Cutie Marks. However, what if they had been able to perform each others’ tasks? What if they had been switched in such a way that they succeeded, despite their destinies being mixed up?
In “Suited for Success”, Applejack mentions Fluttershy’s “freaky knowledge of sewing”. Earlier in the episode, Fluttershy exhibited an impressive knowledge of fashion when she was criticizing the second dress Rarity made for her. If Fluttershy had gotten Rarity’s Cutie Mark, she most likely would have succeeded as a dressmaker. Unlike making everypony laugh, being a dressmaker wouldn’t have conflicted with her timid nature. Fluttershy, like Pinkie Pie, enjoys making ponies happy, but she does not enjoy using the large, highly social, somewhat imposing methods of her pink friend. She would have been thrilled to create beautiful clothes for the townsponies.
Applejack would have been a decent, if not excellent, animal caretaker. As she works on a farm, she knows a lot about animals and their needs. She knows when to be firm and when to be yielding, depending on the situation. Considering her strength, she’d easily handle the bigger, more aggressive animals even without “The Stare”. Her relationship with her dog Winona proves that she likes animals and is capable of taking care of them. More than anything else, Applejack has a very strong sense of family. She treats everypony close to her as if they’re an extension of the Apple clan. This would further hold true for her animals.
Rainbow Dash, as shown in “The Super Speedy Cider Squeezy 6000”, is strong enough to help Big Macintosh run the apple press. At the end of “Applebuck Season”, she can be glimpsed bucking the trees without difficulty. As an athlete, she would be able to handle the work at Sweet Apple Acres. Added to this is the fact that she beat Applejack in a hoof-wrestling competition, suggesting that she is actually stronger than her farmpony friend. In “The Super Speedy Cider Squeezy 6000”, Fluttershy is seen flying into trees to help shake the apples out of them. Being a pegasus, Rainbow Dash could utilize this method if she worked on the apple farm. With her speed, she’d be able to get things done twice as fast. In fact, she might do a better job than Applejack if given the chance.
Although Twilight Sparkle did not get her Cutie Mark switched in the episode, let’s say she did. Her perfect occupation would be controlling the weather. “Magical Mystery Cure” and “Sonic Rainboom” taught us that unicorns are capable of controlling the weather with their magic and they can cast a spell to allow them the luxury of walking on clouds. Twilight is a bookworm by nature who seems capable of learning spells simply by watching others do them, according to “The Crystal Empire”. If she were to become a weather pony, it would just be a matter of research and practice. With her organizational skills and book knowledge, Twilight would exceed at this. The only problem is that she might go “Lesson Zero” on the entire town with catastrophic results.
Rarity likes books, has an eye for detail, and knows magic. Organizational skills seem to be a common unicorn trait, so naturally a unicorn would have to take over Twilight’s post as the town librarian. While it isn’t fashion by any means, she could put her skills to work by decorating the library, organizing the books, and enticing stallions to visit with her flirting skills. As the element of generosity, she would be happy to lend books to ponies.
Which leaves Pinke Pie as the party pony. But as Twilight said in the fan-made episode “Double Rainboom”: “How do you get crazier than Pinkie Pie?!”