Free agent wise, whether or not the money could be worked out, the only bat that interest me is Harper. Machado is nice enough that his splits don't say platoon, but his OBP has only had two good, i.e. > .350, years. He'd bring line up stability, but not enough for my taste.
Bringing back Chavez and adding Miller, hoping he regains form, would make me quite happy. For me, one of the best things about bringing back both Quintana and Hamels is that it either protects if Darvish never really gets healthy this year or just doesn't produce or that one of them, probably Quintana, could be packaged during the season to try to bring another piece back if the team feels confident in the other 4 for the playoffs.
Worse comes to worse, both Quintana and Hamels could make nice trade off pieces if the season goes horribly.