Digging the sketches, I think you are on the right path with the Trickster/bandit setup for the costume.
As far as sensuality/fertility, maybe consider increasing the size of the hips and decreasing the bust size proportionately. Wide hips tend to be more associated with fertility at a base level in the human mind, so you might get more of a primal response out of that.
And I do love your story concept of the two talking to each other but not getting to interact at all due to being kinda the same person, that would indeed be a very fun story to read.