One could fork fibers and have smaller stacks and even make their size dynamic, but actually the number of active fibers per process has been fairly low in all our use cases so stack size was never a concern. The more interesting problem is that of running multiple processes in parallel so you can saturate the increasing number of cores, while retaining low jitter and having a sensible end user API.

My co-founder alexlamsl and I are actually working on something akin to Scala actors for JS that is portable between the browser via Web Workers and the server using Node and Common Node (https://github.com/olegp/common-node). We'll blog about it at https://starthq.com/blog/ in the near future.