Con #1: The Cardinals would be losing a middle of the order hitter who has been relied on to drive in runs
Obviously taking Goldschmidt out of the Cardinals lineup would be a massive loss. In Goldschmidt's full seasons with the Cardinals (excluding 2020), he has hit at least .265 with a minimum of 25 home runs and 80 RBI, that production is very difficult to replace.
Would the Cardinals be willing to sacrifice a little offensive production to make improvements to the pitching staff? It would be a risk no question, because if the pitching struggles again like it did last season, then the lineup would be relied on more to win games, and not having Goldschmidt in the middle of that order, would make that much more complicated to accomplish.
Con #2: The Cardinals don't currently have anybody ready to replace Goldschmidt at 1st base
Looking at the current roster for the Cardinals, they have some guys who could play first base and did so from time to time this season. The players we saw the most at first base when Goldschmidt had a day off were Luken Baker and Alec Burleson.
Baker is coming off a fantastic season in the minor leagues, winning the International League MVP, but he did not see the same success at the plate in the big leagues in limited time. Also, Baker isn't as blessed defensively as the 4-time Gold Glove winner Goldschmidt is so that would be another thing the Cardinals would be losing, as the Cardinals took a huge step back in their defensive play this season.
And then Alec Burleson spent most of his time in the outfield while playing first base on occasion. If Burleson wanted to play every day it would probably have to be at first base due to the current outfield logjam, but has he shown enough to be an everyday player? And some people have thrown around the idea of moving Jordan Walker to first, the problem with that is he has never played first base at the professional level and made huge strides defensively in right field at the end of this season. So do the Cardinals have someone who could play first base every day? At this point, I would say they do not.
Con #3: No Goldschmidt in the lineup could affect Nolan Arenado offensively
Having Goldschmidt out of the lineup would cost the Cardinals an offensive weapon, but it could also have recurring effects on Nolan Arenado. In Goldschmidt's time with St. Louis, he has hit second and third in the lineup, and then Arenado has hit mostly clean-up, without Goldschmidt Arenado would move up to the three-hole, so the question would be who will be Arenado's protection in the lineup.
We saw mostly in the shortened 2020 season where teams did not attack Goldschmidt all that much because he was far and away the biggest threat in the lineup that year, he had limited protection. The current lineup is better than what it was a few years ago, but how many pitches would Arenado see in a lineup without Goldschmidt?
The two best options right now, in my opinion, to hit behind Arenado would be Willson Contreras and Nolan Gorman, Contreras was one of the best hitters in the league in the second half of last season, and Gorman has shown when he's on his game, he's one of the most dangerous hitters in baseball, so it may not affect Arenado as much as we think. However Goldschmidt has been the epitome of consistency throughout his Cardinal tenure, if Contreras and Gorman are as streaky as they were last season, teams may be hesitant towards pitching to Arenado.
Also even if Contreras and Gorman are both going to have strong and consistent offensive seasons, losing Goldschmidt hurts the depth of the lineup. Moving everybody up one spot to fill that void might leave the bottom of the Cardinal order to be less dangerous, because as I said earlier, losing a guy who hits 25-30 home runs and drives in 80-100 runs is difficult to replace.