I'm not sure how this would look very different from current pure functional languages. Think about programming in Haskell. Everything is immutable but you can

I'm not sure how this would look very different from current pure functional languages. Think about programming in Haskell. Everything is immutable but you can compile down to machine level binaries. So at some point the programmer is presented with an abstract immutable model and under the hood some runtime does real pointer arithmetic and all. Even garbage collectors could be optimized already for knowing that the programmer has no knowledge of memory locations. If this kind of OS encourages hardware changes, that's one thing. But aside from performance, it probably won't look too different from current FP languages.