Julien for Frelick would be about fair as fair can get in a one to one trade. I think the Brewers turn this down before the Twins do. Defensively Julien doesn't fit for the Brewers as it looks like Julien's best position is either LF, 2B or 1B. His arm is not good enough to play RF, SS or 3B. He is also limited speed wise so he is stuck at 2B, 1B or LF. Defensively I think he would be fine at 2B but the Brewers already have a bunch of fine at 2B defensively prospects. Bat wise he has more power than Frelick but I think Frelick has the better hit tool.
If I am trading Frelick and it is to the Twins it would be for Lee and not Julien.