Path #2 - Everyday utility option, either at DH or filling in on the field
Should the Cardinals decide to land on a different primary center fielder than Lars Nootbaar, or they decide to trade Tommy Edman this offseason, I could see Donovan being needed as that "plug and play at a different position every day" guy.
If the Cardinals roll with Edman, Victor Scott II, Dylan Carlson, or a free agent/trade acquisition in center field, Nootbaar would be pushed to left field and Donovan would be left without a position on the diamond. That still works out great, as he can be the placeholder at DH each day, getting at-bats there when the whole starting nine is playing, or filling in at a position when guys get days off. Donovan's bat is plenty good enough to fill in there, and it works out great so pretty much whenever someone needs a day off, Donovan is rested and ready to fill in as the first option.
Edman's future plays a big role in this as well. If he's part of a trade to acquire a starting pitcher, the Cardinals would lose his versatility, making Donovan's all the more valuable. Sure, they will still have some mix of Carlson, Burleson, Saggese, Scott II, or even guys like Richie Palacios, Juan Yepez, or Luken Baker to fill roles, but Donovan is the far superior player at this point in his career.
While the Cardinals' best offensive alignment may include days when Donovan is in the outfield, it's likely that their best defense is on the field when Nootbaar is in left field and a more true center field talent is starting every day. With the regression the Cardinals saw from their defense in 2023, there is a strong argument that prioritizing that in a position like center field would be more beneficial than trying to maximize the offensive output each game. Personally, unless Scott II is ready for Opening Day, I think I'd prefer to see Nootbaar in center field, as he is league-average out there and the improved defense of Jordan Walker helps the outfield defense a ton.
Should the Cardinals make that decision in their outfield though, and/or Edman is traded, I do see why they'd like Donovan to be ready for something different each day. But that's the thing - every day. Regardless of the role they define for him, it needs to be every day. If the Cardinals do not get Donovan's bat and possibly glove in the lineup each day, I think they are doing a major disservice to Donovan and the team's success. This leads me to the third and least favorite of the scenarios - maximizing Donovan's value on the trade market.