Spurs don't have to change their entire game plan to use RJ more effectively. Run screens for him, or have him run cuts from multiple angles in the half-court... it should be more effective now that his outside shot has to be respected. If nothing else, it makes the Spurs less predictable, and is one more thing opposing defenses have to watch out for. Last season, the Spurs would run 1-2 plays a game for RJ at the most, usually early. But most of the time, they're still stuck in the Bruce Bowen playbook - make him stand in the corner and wait, switching corners every now and then. Why on earth would you pay a guy $40M for that?
I'm not expecting him to be great, but at least use the guy properly and you might get better results. And he tends to be more energized when they involve him in the offense, so it could have a positive effect on his defensive intensity.
And if that doesn't work, pray that Kawhi is a total badass.