Forget this. A "simple summer strategy" will get this team knocked out by the Conference Finals, at the latest. And maybe any move that they can realistically make will. But you know what? They've clearly made a commitment to Duncan that they'll attempt to contend until he retires. Bringing back the same team that wasn't good enough and having the big three get a year older (while the team that beats them gets a year more experienced, no less) isn't attempting to contend; it's conceding defeat.
Every other contender and pseudo contender is basically going all in. They don't care about "well, what about when (insert veteran star retires), how will we look then?" They're all trying everything they can to squeeze one more le out while said star is around. And that's what the Spurs need to do. If they're going to dip their toes into this water, they better be prepared to jump in.
I've advocated it many times, but always qualified it with something like "it's highly unlikely, but worth a shot"; enough of that. They need to call up Ferry and say, outside of the big three and Leonard, name your price for Smith. Any package of players or players they have the rights to, plus multiple 1sts and 2nds, should be in play. Maybe he still doesn't do it, but he probably at least thinks about it, especially if (when?) Howard consents to go to the Lakers, since Nash can serve as a liaison of sorts between him and Bryant. Once Howard is out, Paul, who's an even bigger long shot, definitely is. And then what does he do with all that financial flexibility? Would Smith, who's apparently back on board, even want to stay at that point?
And let's face it, it wouldn't be the first time in this league that a front office friend did an opposing front office friend a favor. Though Ferry may well have gotten another GM job on his own volition, would he have gotten 6 years and (it appears) full autonomy if he didn't re-join the Spurs and have people seemingly forget the terrible job he did with the Cavs? Probably not. Who knows, maybe he'll feel somewhat indebted to them.