I'm mobile so don't have a good way to just test this myself... Any idea how good/bad base64+gzip is (ie gzipping the json before submitting it)? If it's within a few percent then this probably isn't a bad solution!
The browser doesn't gzip _requests_ by itself, only the server does so with the _response_ if the user-agent (including browsers) states that it supports such content encoding. Of course you can implement gzip in JavaScript, but if you do that, you can already mangle the request and send the file to the server without Base64 encoding.
