I'm not sure how to square those statements with the ones eridius made up-thread that you replied to. There's some very specific downsides to implementing green threads laid out above, which you've done nothing to address.

> no cross-os usable kernel thread standard except fork()

Not to make your own point for you, but fork isn't available on every platform either. Windows has no fork. I'm not sure I consider forking analogous to threading anyways. They are both multiprocessing primitives, but I generally define threading (and it's derivatives) through how it's different than forking. That could easily just be me though.