2. Sell on Jordan Montgomery, acquire a package headline by a top-100 prospect
I honestly think people are going to be surprised at how much value the Cardinals are able to get from Montgomery on the trade market.
No, they aren't getting a top prospect in all of baseball, but with how thin this market is on pitching and how great the need is, I'd be shocked if they do not get a package that is headlined by at least a top-100 prospect in the game.
There are plenty of examples of rentals in recent years commanding a very strong package in return. The Orioles, Rays, Yankees, Reds, Red Sox, Blue Jays, Dodgers, Giants, Diamondbacks, Twins, Braves, Phillies, Marlins, and Astros will all be in the hunt for pitching help, which will continue to drive up at the asking price.
Even if you're of the opinion that they need to resign Montgomery, they should trade him now and look to do so in the offseason, reminiscent of the Yankees and Aroldis Chapman in 2016.