As you know, that ship had unfortunately sailed. Trading Nephew wasn't San Antonio's idea.
I mean, they did. If you're building a defense around Murray, you need a swingman playmaker to handle the offensive point guard duties. There are only a handful of those guys in the league and the Spurs got one.
None of the other trade offers that I heard would have complemented the plan. (Side note: I still can't believes scrubs like Brandon Ingram, Kyle Kuzma, Jaylen Brown, Markelle Fultz, etc. were taken off the table when Nephew was available

... It sucked for the Spurs that a bidding war never commenced but it's also humorous how much other teams overvalued their young talent.)
A lot of people thought Pop could take 12 Steve Novaks and find a way to make the team above average defensively. I don't remember a lot of people pointing out the weirdness of the plan in the offseason, tbh.
Even during the USDA certified, Grade A championship years, the Spurs never went all, all-in. They always had at least a couple youngsters hopping in the popcorn machine.
It was a small-ish sample size but Murray did carry the defense last year at a Gobert-esque level. With him on the court, the Spurs allowed 98 points per 100 possessions. With him off the court, that number exploded to 105.1 points per 100 possessions.
And while we can reminisce about Green and Anderson, the stats say neither one really helped Murray last year. In fact, the defense got worse when Murray was paired with either of those two players.
Again, the plan was to go for a home run. The Spurs thought their one chance to win a championship was for Murray to become an even more devastating defender, so they tried to plug the holes playing Murray more minutes would cause. I'm not here to argue that was necessarily the best possible plan but it's pretty obvious what the thinking was at the time.
1) Flipping Kawhi for an empty scorer like a Kyle Kuzma or whoever while keeping the rest of the team in place would have put the ceiling of the team at about a seventh seed with zero championship potential. That's why I think the Spurs swung for the fences. They could have gone safer routes but none of those safer routes give more upside than simply extending the playoff streak.
2) The Spurs planned as if Murray wasn't a legit offensive player ... or at least they had to cover for his shortcomings. Players like Green and Anderson fit next to Murray defensively, obviously, but would have been a difficult fit offensively. For example, in a vacuum you pick Anderson over Bertans -- but with Murray in mind, you have to pick Bertans over Anderson.
3) I never heard Beal being available for Kawhi. But even if he was, that would have been an awkward fit since you'd then have to believe Murray is a legit playmaker. If you trade for Beal, then you basically have to pivot away from Murray. Even in the scenario that the Spurs bring back the same team plus Beal, that's still a relatively low ceiling team considering Murray would be stuck playing 20-22 minutes again.
4) The Wizards act like Beal is their franchise player and Wall is the one they'd like to trade if they could. To think they could have gotten Beal from the Wizards while also offloading Gasol on them is ... wishful thinking, IMO.
Agreed. I think Pop saw White and Walker and thought they could replace Green and Anderson. White is smaller than Green but he plays bigger than he is so he has across the board defensive potential. And then on the offensive end, he fits today's need for penetrators with good court vision. Pop also dropped hints from Day 1 that Walker wasn't going to be the typical redshirt-in-Austin rookie.
I don't know of a team outside of the Bay Area that isn't left vulnerable after one of their top three most important players is lost for the season. In San Antonio's situation, they bet big on Murray taking a big step forward and constructed their roster with that in mind. The roster obviously looks "weird" now but that's because the player the team was most built around is now lost for the season.
I don't mind people criticizing the roster construction (personally, for example, I was in favor at keeping Green at nearly all costs and keeping Parker around). But I do think it's disingenuous for people (not saying you, particularly) to criticize the current state of the roster while ignoring that losing Murray totally changed the equation.
Cunningham wouldn't be anywhere near the starting lineup with Murray around. He was signed as deep reserve big who got thrust into the starting lineup because he was the only thing left around that looked like a possible defensive player after Murray went down.
I don't know how Murray and DeRozan would have fit but I image Murray would have ceded most of the playmaking duties to DeRozan. But, again, your point on how the offense looked like it would struggle is exactly why the Spurs opted for offensive role players rather than defensive role players.