#4 - Do nothing
Luckily, I do not see any scenario where the trade deadline comes and passes and the Cardinals have made no moves. Mozeliak's comments indicate that strongly.
""We know we’re not where we want to be. We know we have to make some changes. We’ll try.”"- John Mozeliak
There have been deadlines in the past (see 2017) where the Cardinals sat back and did not make a single move. Sometimes the club makes a series of smaller moves (J.A. Happ and Jon Lester in 2021), and sometimes they go and make some bigger swings (Harrison Bader-Jordan Montgomery in 2022).
This year's deadline will likely see the Cardinals make more moves than they've made in recent years (more on the specific moves later). There are just so many potential ways to capitalize on value, or improve this team, that they'll be able to pretty easily find moves to make.
I don't have a ton more to say here, because the real meat and potatoes come from the other three scenarios.