For mining on steem even a wifi connection might be too laggy... Even an adequate ADSL connection might hold up packets long enough for you to miss a block. Tor? no, really, it can't be done. You just never know exactly when you will get the job. It might coincide with all kinds of things on less than optimal connections.

My scheme would allow anonymous account creation via tor connections to an exchanger and payments initiated via tor. @someguy123's anonsteem site you can more or less do the same thing as well. But on-chain means nobody has to do it and thus also nobody will charge a premium.