Hi, I understand what you are trying to achieve, but i don't think you'll get what you want, in the end. A proxy, provides two major functions:
* proxies client requests
* caches some of the responses
However, please note that not everything gets cached (site searches, dynamic pages etc) don't get cached that good. Usually you cache static html pages, images, css, js files, mostly stuff that doesn't get changed too often. But submitted forms might not get cached, so in this cases, the requests might get processed each time.
As for the routing part (OSI Layer 3), this might help you if you have multiple ISP connections and need to instruct the routing mechanisms to pass certain packets over certain interfaces ... but once your packets get routed through the interfaces, you can't do much to them. The other internet routers determine how your packets get routed to the final destination ....
If you have questions, let me know over the chat.