It's not arbitrary, it's simple math. 32xxx discrete values is the precision limit for 16bit integer calculations and AE is build around that in a lot of areas. After all, it was conceived over 20 years ago when computers could barely handle even a single HD frame. With that said, there can be no such thing as some magic switch, registry tweak or whatever. You would have to rebuild the app from the ground up to bypass these limitations, which of course is happening here and there, but even so - since many algorithms, image formats and so on are build around similar logic, there can be no universal "one fixes all" solution. And for panoramas/ VR and so on there are better ways to solve the issues, anyway, from a technology point of view. AE just doesn't have any of that yet.
There are also specific frame sizes for video based on compression algorithms. You'll have to break a 30,000 + screen size into smaller segments to play back the project anyway. I've built multi screen presentations for about 40 years and working around the limitations of projection is always part of the workflow. It's not that hard to match up edges or prototype with smaller frame sizes so you can get things in sync. It just takes a little creative problem solving.
I have a very similar question and am wondering if there's a clearer workflow recommendation. I have need for a comp that is 67k wide, but only about 10% is actual projection surface. Just trying to create a template for designers so they can work with negative space and move objects through the room at correct scale etc.
My workflow is usually:
Master Comp that represents an entire space.
Render Comps that refer to the Master comp and render specific screens.
But I'm having trouble conceptualizing a solution here. Do I build everything in 1/4 scale and then scale up on the renders? Then the final resolution will be quarter resolution scaled up which won't look great.