I don't think they give SGA a year of being a secondary facilitator to learn from CP3, then go back to making him a secondary facilitator to Ben
Unless they really believe in their coaching and think they can mold Ben into being an off ball wizard that does the Draymond type things (which he could). I think if they took that contract, they'd do so thinking that he'd work out well while Kemba would just be (hopefully) rehabilitated to where he could be flipped next offseason.
If they win the lottery, SGA is a secondary facilitator to Cade, and whether he translates as a PG to the NBA is TBD.
What I'm saying is that OKC is kinda turning into basketball rehab for guys since all they work on is player development, and since nobody thinks they'll ever cash out for a superstar or use all those picks, might as well use it on Ben Simmons. It's a no lose situation. If he doesn't fix his issues, Presti got a war chest of assets to replace him. He doesn't hurt their cap, but if he fixes him, Simmons will be in OKC for life all while pissing off the rest of the league.