Running code under a different user is hard. I don't know how I would do that on macOS, and the times I've done it on Linux I've always had to jump through a bunch of hoops.
MacOS aside, as this is not a serous operating system for this kind of workloads, do you think the "hoops" (which actually?) one needs to "jump through" are so problematic that it makes sense to create millions of lines of new code just to work around them? Only to arrive at the same result that is already working since something around 50 years? This must be really grave issues with just running a task as a different user… Could you expand on that?
I want to write software that end users can install on their own machines, that supports plugins so they can execute additional code from untrusted sources.
So macOS needs to work.
Microsoft Flight Simulator uses WebAssembly for its extensions system. I want to do the same thing for my own projects.