[dreish]

I've been thinking along the same lines for the last few years. If you did this, you could have a multi-user operating system in a single address space and avoid the cost of interrupts for system calls (which would just be like any other function call).

[0x0]

Sounds similar to some ideas explored in the experimental OS "Singularity" - https://en.wikipedia.org/wiki/Singularity_(operating_system)