[_pmf_]

> All those other dynamic scripting languages? They're DOA because nobody's going to download the entire VM every time.

Hosted on a CDN in compact form, it'll be feasible; application can just link against it, it does not have to be recompiled on the user's machine.

> Very problematic because the toolchain relies on LLVM-like semantics which don't like good garbage collectors or functional programming in general.

That will indeed be a problem. The design restrictions imposed by the environment (continuous heap, emulated concurrency) will bite us in the ass hard. Instead of layering a lot of very leaky, performance killing "security" features over other half assed features, a better way would be to step back and use a tiny hypervisor. That way you have hardware accelerated memory safety, but it would require the application to be able to run in a microkernel; recent IncludeOS + ukvm has a boot time of 11 ms. (Great, now I want to write a plugin that embeds qemu in Chromium and uses a virtual device to communicate with the host.)