What do you think an Unexpectedly Dark Episode version of a My Little Pony: Friendship Is Magic movie would be like?

Don't know.

6853201 I imagine for starters they would go into a lot more detail about the Storm King and why he's so feared. Expanded media paints him as a mericless tyrant with Tempest as his enforcer, and a tie in chapter book suggests that Tempest attempted to steal the Pearl of Transformation on Mount Aris but was found out, and the hippogriffs fled when they learned she was working for the Storm King. It's not hard to imagine the movie with a darker tone suggesting that the Storm King personally hunted them down, and that Novo is afraid to go back on land in case he's still around.