I don't think you should consider Sam's line the "top defensive unit." This team's optimal performance has been with Reinhart keying more of a second scoring line and Casey getting in where he fits in.
I also don't think we have the wings to shift Reinhart to center, especially if Sobotka is one of those options. Sam has been excellent at finding soft spots behind the coverage in transition, and I don't think that Vlad does those same things even with 23 improving the quality of service. His defense from the wing has been good enough to compensate for iffy center play, and his offense definitely benefits from being further up in the play, so idk if that trade-off is worth it until the team trades for a Saad, Niederriter, Krieder, Stone, Tarasenko, etc.
Both Sobotka and Erod are 60% goals players with Sam, as is Thompson. I think ERod is clearly the best of that group, but either way, there's your rotation.