Here's the problem I see with this. The spurs have been steadily grooming guys who by all accounts are ready to step into that role that RJ was supposed to have provided but didn't. And they would have been much better at it.... most notably Gary Neal & Tiago Splitter.

Now instead of those guys stepping up and going 8-15 for 20 pts like you said we'll instead be treated with a typical Stephen Jackson 5-18, 15 point night instead. And most likely losing those games.
Per the usual your not getting it. Replacing RJ with Jack is not going to stunt the growth of Leonard, or Green. Jack is a proven playoff performer, who provides a toughness the Spurs have been missing for awhile. I don't care what kind of stats Jack has. He provides the competativeness factor that RJ has never shown while in a Spurs uniform. Or in other words, Jack is a baller, while RJ has turned into a marshmellow.