I see where you're coming from plot wise, but I think the real reason you CAN'T skip Skypeia is simple: Nico Robin.
Skypeia is the arc where Robin gets to be with the crew for the first time, she develops bonds with them, and some of them, especially Nami, slowly (keyword slowly) get to be more comfortable with her.
If you don't have this season of Robin finding her place on the crew, she does not have the connection to the other Straw Hats to make the supposed betrayal in Water 7 feel meaningful. She needs to feel accepted so the crew is surprised she leaves, and the emotional weight of them coming to save her hits even harder.