That wouldn't be a 100% match since it assumes HTTP headers and mangles them, too. For example, it probably uses the MIME type served by the proxied server to see whether it's css or js or whatever should be minified (I didn't check the sources for this).

With a pipe, it'd need to use heuristics to figure out what kind of file it is. That could be added, probably, but it's not entirely trivial.

Additionally, you'd miss out on all the HTTP header mangling, such as cache expiry settings.