> Assuming those requests are sent in order

That's the problem right there. Right off the bat I don't see how to get around that one.

They'd also have to be all on the same connection. Also, you'd lose out on caching.

At that point you might as well just inline the css and javascript.

Dynamically generated unique hostnames per resource would work.

I'm probably missing something but... wouldn't all the extra dns lookups remove most of the speed advantage?