preamp grounding question

So on a preamp when you mount the pot to the faceplate, whichs how it is most of the time, the chassis has to become a ground plane inevitably because the casing of the pot has to be grounded also.

My question is would it be better to somehow isolate the pot from the chassis (i can think of several examples) so that the chassis can be an earth shield instead?

2nd question regarding the pot's casing being grounded- for a true mono mono psu how would this be configured if i want the ground between L and R completely separate? The pot's casing is usually one piece.