I'm not wed to the idea of a three-point bomber big guy, but you need people who can shoot similarly to the people they're replacing if you're doing a "system" offense. In the case of TRob and Frye, you'd reverse who they sub in for, and play them as a burly body (Robin/TRob) who can do the pick and roll, and a willowy midrange shooter (LA/Frye). Freeland and TRob are two poor shooter with no range together, and the system fell apart, because no matter how well Mo emulated Dame, or Barton/CJ emulated Wes or Wright emulated Batum, the lack of spacing because nobody needed to really defend Freeland/TRob hurt. Frye helps that by keeping defenses more honest. Spacing spacing spacing.
I bet adding a legit shooter at the PF position and keeping everyone else the same would see our bench improve just because there'd be less need for Moffense, fewer broken plays, and more offensive consistency as players are brought in and out gradually.