I run
Fatal Push and
Hidden Stockpile. The first one is really solid removal, the second one is a really fun build around. When I still supported
I also cubed
Renegade Rallier, which is also really neat. It can even get back that fetchland you just sacced! I tested
Vengeful Rebel, which proved to be a bit harder to properly use, but it's good in aristocrat decks.
Narnam Renegade also is a solid enough one drop, in a fetchland heavy environment it's basically a better
Kird Ape. Lastly,
Solemn Recruit is an excellent card. I cut it because I tried to support humans, but I've since abandoned that tribe, so maybe I should make room for her again!
As for your suggestion,
Greenwheel Liberator has been a bit underwhelming, because all it brings to the table is stats in a color that has more reliable ways to put big two drops into play. Green also isn't a good fit for aristocrats, so often it just sat in the hand as a very underwhelming 2/1, whereas it's perfectly fine to run out the Renegade as a 1/2 deathtouch, since it will still trade with an opponent's creature.
Edit: Oh, one other excellent card I forgot to mention is
Countless Gears Renegade, I've really enjoyed the card when I had it in my cube. It's both more at home in its color's typical archetypes, two bodies often are more relevant than the additional power, and white is a more logical pairing for the aristocrats colors than green, since it's naturally adept at flooding the board with fodder. Man, I should really find a way to reinclude that card, it was gas!