They could design house space into new lands/ride buildings. A multi story building with a floor dedicated to overflow queue could easily be designed to have that space be used as house space.
Some of the back of house area would have to be preserved, but a lot of it could be shifted to other parts of the property if push came to shove.
Uni owns plenty of IP's to replace KZ between illumination and Dreamworks.
I agree that they need to diversify their rides in the park. A Shanghai pirates type boat ride with more water effects and a splashdown would probably be ideal, but who knows if they'd build that.
My point was just that they don't have to limit themselves to the "Kidzone", "Simpsons", and "MIB/FFL" areas divided as they are. Everything in there is semi-expendable. The logistics of the FFB building probably prevent a complete restructuring more than anything. That's not a cheap building to replace, and even if you do, whatever you replace it with will have the same needs and obstacles.