It is not possible to build a rule to gzip the data. :-/ (https://community.mcafee.com/message/202364#202364)
If transaction goes through the MWG rule engine it will follow that process (not compressed on client side).
It may be possible using the file server, but I have not tested it.
If you use the file server, it still needs to process through the proxy to replace the body content dynamically, and even if it gzipped from localhost to the proxy, it would still be uncompressed from the proxy to the client
isn't the proxy.pac file cached on the clients and only transferred every now and then? So I would expect the Proxy.Pac to not cause a lot of traffic.
we diskussed this feature last week at the inner circle meeting in Unterschleissheim/Munich. There is a way to generate a PAC File dynamic using some nice features like Body.ToFile Event and so on. :-)