Shouldn’t have picked Sessions on of the boys in the first place ,should have picked an outside
Wouldn't have made much difference from a "political optics" or "bias optics" point of view. The position inherently has a conflict of interest. See Lynch vs. Obama, and she was an outsider. So was Holder.
Separately from selection in the first place, assume for talking purposes he fires Sessions. Anybody he picks for replacement will be picked because they will go after Hillary, and they will spike any investigation into the Trump campaign. True or not, this is what will be asserted as truth. The replacement will have as much or more bias baggage as Sessions has.