Shogo's arm looked pretty good out there. Certainly good enough that I'd put him in right on Castellanos' off days/DH time, without hesitation. Not sure I'd go through the trouble of switching him and Llanos permanently (we need to be careful not to bruise anyone's ego), but I feel comfortable with Akiyama handling all three OF positions.
Grading Shogo from the 50 or so games I watched with him last season, I'd say he's got a neutral range/arm but impeccable instincts and great hands. He just seemed to be positioned well every time the ball came his way and never missed a play.
I like the idea of Naquin getting the 5th OF spot over Aquino, and agree with mth that AA's defense has been disappointing. Naquin/Senzel/Shogo would give them 3 OF who can play all three spots in a pinch, plus Winker and Castellanos. Ideally they add the DH and Winker/Castellanos take the lion's share of reps there.