Rewriting Javascript w/o APM

Not sure how far you've gotten with the STREAM profile approach, but that is probably your best approach.

    when HTTP_REQUEST {
        HTTP::header remove Accept-Encoding
        STREAM::disable
    }
    when HTTP_RESPONSE {
        if { [HTTP::header Content-Type] contains "text" } {
            STREAM::expression {@realserver@server@}
            STREAM::enable
        }
    }

You may need to fine tune this search-replace, but the idea is to replace any instance of realserver in the response with the external server name. If you need to also rewrite complex URI patterns, you may want to consider either the ProxyPass iRule (11.3 and below) and rewrite profiles in 110.4 and above).