Option #4: Sign an external free agent
If the Phillies plan on moving Harper back to the outfield, this becomes a very clear option for Philadelphia to pursue. Rhys Hoskins is likely their top priority, but what if he chooses to sign elsewhere? There are still some decent options they can bring in to play first base.
Josh Bell had an outstanding second half to help the Marlins squeak into the postseason. We know what happened after that, but Bell was a staple in the middle of their order down the stretch after they acquired him. Philadelphia bringing in the switch-hitting first baseman, who just so happens to have an .889 career OPS at Citizens Bank Park wouldn't be a bad move at all.
Brandon Belt got off to a slow start in 2023 and was primarily a DH for the Blue Jays, but he finished incredibly strongly and was consistently hitting second for the Blue Jays as they made the postseason. The Phillies could sign Belt to play first base against righties, and use Alec Bohm at first against lefties with Sosa filling in at third. Belt had an .890 OPS against right-handers this season and would obviously provide a big boost offensively. This is, of course, if he elects to play in 2024 and not retire.
Former Phillie Carlos Santana is another guy the team could bring in to play first base. Santana wound up playing a key role for the NL Central champion Brewers after they acquired him. He'd played an above-average first base in 2023 and would be the lone switch-hitter in the Phillies lineup.
If Hoskins leaves, the Phillies most likely wouldn't be looking at a guy like Cody Bellinger to fill the void, but there are still some solid short-term options for Dave Dombrowski to consider.