Not going to get too in depth with actual data here, but I'll start with something.
Miguel Sano is projected to be at -14 defensive runs at first base in 2022. To be clear, I'm not talking about positionally adjusted defensive value. I'm talking about defensive runs specifically at first base. After positionally adjusting, we get a crisp -27 defensive runs for Sano in 2022. His offense would have to be tremendous in order to justify playing time. He's not a terrible hitter; he is pretty good, but not nearly enough to be a good everyday starter. That is unless, of course, we think outside the box.
One positive in Sano's game is his cannon of an arm. The behemoth of a ballplayer can sling it. The 6'4", 280 pound man is also not notably slow; his speed is below the league average for sure, but he's not Albert Pujols. The question is: can the guy play right field? The short answer is not really. He certainly wouldn't be a good defender in right. The real question needs to be: is Sano's value maximized playing a corner outfield position?
Miguel Sano has played 312 innings in his career in right field, and they came in 2016. He didn't exactly impress. A -6.7 UZR/150 indicates that he would be around -14 on defense, which is a massive boost as compared to his abysmal time spent at first. Just for reference, his -17.9 career UZR/150 at first is even worse than his projected total of -14. It's worth noting that Sano was 23 when he played in right, and was much faster than he is now (well above league average, actually. The dude used to be a shortstop. Absolutely insane.) Sano would probably be a lot worse today, but the samplesize is also ridiculously small, so I wouldn't necessarily count him out in right field.
You might be wondering: "Why not put him at DH?". This is a great question. He definitely should play DH. Unless he has some untapped potential in right field, DH is a perfect spot for him. There is no reason to make him worry about fielding; just let him hit. However, if there ever is a scenario in which he does need to play the field, it should not be first base. I cannot understate just how atrocious he is at first base. Psychologically, it might make sense to put the big lumbering power bat at first. This does make sense if he is an unknown quantity. Usually, when a player moves down the defensive spectrum, he improves (or at least holds his own, because moving down the defensive spectrum implies regression. Regardless, players should do better at easier positions.) This is not the case for Sano. Sano cannot handle first base, and would be better off playing a more conventionally difficult position. This would allow the Twins, or any team employing Sano, to get a conventional first baseman that can hit as well as Sano while also not being a liability out there. Those types of players are relatively inexpensive due to the surplus of good hitters that are not athletic enough to play the rest of the field effectively. Just look at how CJ Cron has been paid over the years.
This applies to a few other guys. Josh Bell is another main example, since he is just a less exaggerated version of Sano from a value perspective. Bell has been considerably more atrocious in the corner outfield than Sano has, so Bell's value is probably best maximized as a DH. Then you have a guy like Bobby Dalbec, who is a potentially skilled defender that just hasn't gotten acclimated to the first base position. As a natural third baseman with fantastic athleticism, it might make sense for the Red Sox to get Dalbec off of first. They could try Rafael Devers at first, since he doesn't exactly handle the hot corner very well. They could also just trade Dalbec to a team that doesn't have a third baseman, maximizing value for both sides.
The point of this post was to demonstrate the opportunity cost of having an awful defensive first baseman. There is a reason that the DH position exists, but there might be other alternatives as well in the case of an emergency. Just refer to the title.