Fibers (or equivalent constructs) aren't supported by all the languages that Vert.x supports (e.g. Java) so we can't really support something like that until we can do it in all the langs.

I know Fibers/Green threads are all the rage right now, and it is certainly something to keep an eye on, but I am not entirely convinced that roll your own threading is going to be any more performant than what the kernel can do.

If we can find a way of implementing fibers efficiently, that supports millions of fibers on a single JVM instance, I would be interested.