Do you think that forcing Devers and Casas to split DH time so the team could offer more playing time to Gio Urshela wouldn't be an issue for Devers or Casas? Not to mention, the goal with Casas HAS to be to have him play as much first base as possible in order to get better there, both for the Red Sox and for his career.
These are people, who have goals and futures in this, or another, organization. It isn't MLB The Show where everything is ones and zeroes. Urshela wants to get another contract after this one, after missing half a season with a broken pelvis. He wants a spot he could play every day, and there is no world where the Red Sox were going to guarantee him that, and I don't blame them, even a little bit.
I want Devers to improve at 3B, but he is already unhappy going into this season so I don't see how pushing him to more of a DH role would improve on that attitude, either.
Anyone else on the market, at least the offensive players that are left, is a marginal upgrade at best. They might be a slight improvement somewhere (Urshela probably is an improvement on Reyes, assuming he comes back healthy), but there aren't any true "holes" that they need to fill.
I hope to see another SP added before the season starts, but I really think the offense is what we can expect to have out there on Opening Day for the most part.
I voted none of these, FWIW.