I understand the logic behind it, but how effective is a lineup full of platoon guys in the age of openers? Your platoon advantages get blown up by the second half of the game.
If these were one-position type players who hit righties or lefties well with the aim of putting together stacked RHH-heavy or LHH-heavy lineups against starters, then I would agree: openers undermine the platoon strategy.
But Santana and Marwin are seven-position switch hitters with tiny splits. They make us
less brittle. Like, the whole point of Marwin Gonzalez is that he has a league average bat (99 career OPS+, a bit better some years, a bit worse others), no appreciable platoon split, and he can play acceptable defense at any position. If Santana pans out, he'd be the same way. That's the opposite of a specialist strategy.
We're likely to have a bench that will put Cora in a strong position to reorganize on the fly in more subtle ways. You could, say, bat Arroyo for Franchy against a tough lefty with runners on, and then move Kiké from second to the outfield and leave Arroyo at second. Marwin and Santana are both true switch hitters; they could sub in for Renfroe or Dalbec against tough righties. It's also worth noting that we are also likely to have one of Franchy, Dalbec, or Renfroe on the bench most games. That's a lot of power, and being able to PH a hitter with that kind of pop could really help in situations when we're down by a few runs but have runners on. Then we can use our positional flexibility to rearrange an effective defense afterwards.