I had an idea for an alternate universe where this was the case.



Applejack stays in Manehatten for a few weeks after the rainboom, but still ends up returning to Sweet Apple Acres, deciding that city life isn't for her. The return doesn't get her a cutie mark, but when she gets injured and laid up for a while, one of the books Granny Smith borrows for her (not reading the title) is about magic, and AJ gets inspired by it. Wanting to figure out magic is what gets her a cutie mark, and as a result, she's happy enough to overlook the fact that her injury never properly healed and she's left with a limp.



Fast-forward a few years, and she's figured out enough about how magic works to be able to start making machines which can translate earth pony magic into something similar to unicorn spells. Her inventions revolutionise Sweet Apple Acres, but they're still fixed-function devices. The first general-purpose one fills a whole room, but by the time Twilight gets sent to Ponyville, she's gotten it down to something which can be worn like a pair of saddlebags. Twilight, of course, is fascinated with Applejack's work and the two spend lunch talking way over everypony else's heads.



That's about as far as I got. I was trying to come up with an alternate universe where Applejack could get the Element of Magic and I ended up coming up with that.