The problem here is that special relativity (at least in the basic cases) really doesn't contemplate rescaling things under your own power. If you go really fast, it can cause things to appear different sizes (indeed even be different sizes, there's a cool problem where a 1 meter stick shaped like a T can push a switch inside a 2 meter hole shaped like a U). It can't compare when different frames are also using different units, however.

Basically, all reference frames must agree on the meaning of units. Although Frame A might observe the stick and say "that is 1 yard" where frame B does not, they both understand the words "1 yard" to mean the same thing.

Jade's scaling abilties throw this out of whack. 1 yard on one of the planets is NOT the same thing as 1 yard on the battleship, which is NOT the same thing as 1 yard to Hussiebot. This difference would exist even if all items on screen were standing perfectly still in the same reference frame.

This difference makes comparison between the planets, the battleship, and Hussiebot impossible as presented. You have to select one frame's units and apply them to every frame to have a meaningful comparison. For example, if you use the kid's frame then the battleship is a maybe a few hundred yards long, Hussiebot is the more than 1000 yards tall, and the planets are a few inches. That allows for meaningful comparison.

@Draconi: but...but I spent two years of undergrad studying this stuff.