It's a fairly widespread idea for architectures that try to move things out of kernel mode. The Hurd does program image file loading in userspace, too, in its exec server(s).
The tricky part is setting up the initial process. The way out for that is static linking and re-use of the fact that the operating system kernel loader has to understand and be able to load (at least a small subset of) program image file formats too.
It's a fairly widespread idea for architectures that try to move things out of kernel mode. The Hurd does program image file loading in userspace, too, in its exec server(s).
The tricky part is setting up the initial process. The way out for that is static linking and re-use of the fact that the operating system kernel loader has to understand and be able to load (at least a small subset of) program image file formats too.