I think the upped is a bit too strong. Maybe if it randomly shuffled creatures to your benefit, instead of an outright exchange.
The exchange idea is nice, but, building a deck around this, it would be too easy to abuse.
I think it fits best in aether. It's not like every card that does something randomly is entropy and can be seen nowhere else. I'm not sure where that line of thinking comes from.
But all all out switch, way too easy to flood your field with malignant cells (or just play nothing), then, when the time is right, swap creatures and end up with the field they have been building all game, leaving them either locked with 1/1 creatures, or with just nothing.
Maybe if the first were to randomly swap creature positions, while the upped were to randomly move creatures? The first would then make for a 100% fair exchange, and the second would, in theory, cause a 50/50 spread on the creatures in play, so not allow anything quite as extreme as a flat out exchange.
I don't know how the current mechanics of the game would work in practice with reassigning spots randomly. For the ideal situation, it would have to act as if it picked up all the cards and reassigned them places one by one onto an empty field. Otherwise, a field with lots of creatures could really skew the position assignments, which may actually not be a bad thing, either.