I really expect an exceptionally efficient year out of JO. This is a team where he'll be a 5th option - and I think has the players that he can accept being the spare tire for. Doc has shown to be really good at getting head strong guys (Pierce, Rondo, maybe Ray) to play the way the team needs most of the time.
He may not have better post iso than Perk, but he has better hands by a million and shoots much better at the FT line. This will make a big difference as Perk got a lot of dump off opportunities that should have been easy buckets or free throws where he either turns it over, misses the shot, or misses the free throws. These two will be a great platoon at Center once Perk is healthy, and JO is a good insurance policy if that doesn't happen. Also the fact that all big pairings (between the expected top 4 guys in the playoffs) will work well, is a bonus. (Perk/KG, JO/KG, Perk/JO, Perk/Baby, JO/Baby, Baby/KG -- all work.)