He needs to keep working on his hitting and his defense at 3B, SS, and 2B, which isn't light work. IMO I don't see a reason for him to put work in at 1B given all the other options there. He could grab a glove and take some reps in CF/OF (which he seems to be doing already thanks to footage someone posted on social media), but I don't see 1B as a position that's going to be needed for him. At most maybe CF in a pinch.
Between having a short ST due to injury and the early Opening Day in Japan, plus having to significantly retool his stance/approach in the middle of the season (bigger changes than PCA or Amaya were asked to do IMO), plus still learning a relatively new position at the MLB level, I think Shaw was asked to do a lot as a rookie last year, and did an ok job at it. He still has work to do with his hitting, I worry a bit about his plate coverage, but IMO we don't have much of a grasp on what he can really do at the plate. He was a very good prospect with a lot of success at every level below the MLB.