https://www.printables.com/contest/449-framework-computer-mainboard-case
A while back they partnered with Prusa on a 3d printing contest. There are some neat cases in there, including a steam deck style one, but no direct laptop replacement.
It wouldn't be THAT hard, it just seems like nobody thought it would be useful, you wouldn't get any additional functionality out of a bigger case, you're still locked into the same connectors, battery, and modules.