My mind is sort of blown by how many people think Simmons wouldn't be a massive upgrade over any player on the roster. I do think there's a limit to what the team can trade for him, but it'd be easy to make a playoff team around him. The only player who'd even have an argument against him is a fictionally fully healthy Derrick White. Theoretically, the Spurs could trade Murray, Poeltl and incentive to take Simmons into cap space. If they then do the DMDR for Kuzma/KCP trade, they'd have up to $10 Million in cap space. Earmark the room exception to bring Dieng back, draft a center like Queta with the not-12 pick (28 in my Capulator mock-up),and you have a pretty chunk of coin to add shooting or even bring Mills back. Round out the roster buy locking up Weatherspoon and KBD to long-term cheap deals, and you get:
White, Mills, Jones
Vassell, Walker, Weatherspoon
Johnson, KCP, KBD
Simmons, Kuzma, Samanic
Dieng, Eubanks, Queta
I'd prefer to swap Mills out for a capable guard who can run an offense when White is hurt, but Patty should fit well with Simmons, and the culture and all that. An alternative to either Kuzma or Caldwell-Pop could be a Schroeder S&T, but I'm not the biggest fan of that. Maybe the Spurs could take back Hill in the Simmons trade while the Lakers sent Dennis to Philly? That might actually work better, and it would be fun to have George back after the last few crazy years to his career. They'd have to find a rotation-caliber forward with the salary saved though.
White, Hill, Jones
Vassell, Walker, Weatherspoon
Johnson, (FA Wing), KBD
Simmons, Kuzma, Samanic
Dieng, Eubanks, Queta
Or other combos. Either way, I think a team built around Simmons is functional and better than what SA is running with currently. It'd not hard to have good spacing if you don't devote like 60 percent of your minutes to non-shooters. Swapping out Jakob for Dieng or another stretch-five is crucial, so keeping White and Vassell becomes a huge deal, as is getting a guy to spell White and take over for Dieng as he stops being even a technical starter. The center problem would likely need to be addressed with the MLE the following season