The Cubs are in a really fascinating place right now. Let's assume that Cody opts in, which is likely at this point and they don't move Taillon. They're going to have something like 40M available in FA. As of right now your 2025 Lineup probably looks like this
C-Amaya
1B- Busch
2B-Nico
SS-Dansby
3B- Parades
RF- Bellinger
CF-PCA
LF- Happ
DH- Seiya
Improved, absolutely but still lacking at least 1 bat. The most obvious thing to do would be move Bellinger to center, PCA to Iowa and find a Rfer.
As far as the rotation goes, you could completely justify not spending a cent on it. Steele/Shota/Taillon/Assad/Wicks/Brown/Wesneski and eventually Horton is really solid and has good depth. Even with Bigge traded and Neris likely gone, would the pen need more than 1 arm in FA, if any? Merryweather/Adbert/Leiter/Little/Hodge/Miller are all legitimate arms and you may have Pearson too. Basically, how are they going to spend this nearly 40M? I know it's not going to happen, but this is about as perfectly set up as they could be to add a guy like Soto. RF/C are really the only 2 must spend positions as things stand and C could very easily be solved through a trade.