Since it's for a wall-hanging swap, could you ask your swap partner what space they have to accommodate it? (I'm sorry I'm not familiar with that swap, if it's the kind of thing that's all-surprise or if there's communication between known partners.) If they have the room, I'd upsize it. If not, I'd finish it as-is.
My vote is also for no sashing. The subpatterns are really evident when the blocks are together. Your quilt looks really cool!