I'm hoping (as others have suggested) that Hanley and Ortiz also figure into this rotation, so that in addition to the ABC options that GNQ suggested we also occasionally see
D Betts, Castillo, Vic
with Hanley sometimes out of the lineup and sometimes replacing Ortiz at DH. That would get Betts/Castillo/Vic a little more PT, help the defense, and rest Hanley/Ortiz.
In this scenario, Nava is just the 25th man; he mostly spells Nap at 1B, pinch-hits occasionally, and once or twice a month gets a start in the outfield.