Got a script using Savon 2 with the e-conomic SOAP API (a 3 MB WSDL) down from around 30 seconds to around 2 seconds by marshalling the Wasabi WSDL parser. Consider this a proof-of-concept.

marshalling_wasabi.rb

# For Wasabi 3.0.0.
# Marshals WSDL for a huge speedup with large files.
# A 3 MB WSDL went from around 30 to 2 seconds.
# Marshalling: 3.1 MB -> 629 KB.
# Zipping: 629 KB -> 59 KB.

module Wasabi
  class Parser
    alias_method :old_parse, :parse

    def parse
      old_parse
      # The Nokogiri document prevents marshalling.
      # We've parsed so we don't need the document anymore.
      self.document = nil
    end
  end

  class Document
    alias_method :old_parser, :parser

    def parser
      return @parser if @parser

      @parser = load_parser_from_marshal

      unless @parser
        old_parser
        dump_parser_to_marshal
      end

      @parser
    end

    private

    def load_parser_from_marshal
      if File.exist?(marshal_file)
        Marshal.load(unzip(File.read(marshal_file)))
      end
    end

    def dump_parser_to_marshal
      data = zip(Marshal.dump(@parser))
      File.open(marshal_file, "w") { |f| f.write(data) }
    end

    def zip(string)
      Zlib::Deflate.deflate(string)
    end

    def unzip(string)
      Zlib::Inflate.inflate(string)
    end

    def marshal_file
      basename = File.basename(@document)
      "./#{basename}.marshalled.zip"
    end
  end
end

And around 60 KB zipped. If that doesn't slow things down measurably, it could keep the file size down even more.