I've shot quite a few interview setups like this, and I like using a slider on B (or C, if you have a wide and close straight-on). I find that shooting the moving camera further off-axis helps a lot in the edit, at at least 45 degrees (further if it works with the tone). That way it feels like a narrative choice, and doesn't just feel like a more dynamic version of the A cam shot. Also, being further off-axis helps the A cam shot keep its energy, since it's the most connected with the subject.
Edited to say: I agree, it's harder cutting a handheld shot in than a slider, since I think there's a much bigger energy shift cutting to handheld.