Is there a tool / browser extension to exclusively view lightweight, preferably plaintext version, of websites without relying on Google's servers for proxying?
There are many terminal based browsers like Lynx, Links, Links2, w3m, elinks, etc.
I also just ran across this, which I haven't tried, but looks interesting.
Firefox mobile can turn off images and web fonts and JS, that's more or less it unless you have a faster host somewhere else that can download and compress for you.