Double serving the AG as something else will invariable risk a conflict of interest at some point regardless of what post it is. I think we should look at it in terms of systemic risk, what could a VP do as VP that also being AG could allow for him to get away with that he would otherwise be charged for?
A good point. The President could appoint a special prosecutor to charge the AG, but we would be demanding that the President pay close attention to affairs that may be tangential to what he does.
A potential idea for making the chief executive more powerful: eliminate the AG and vest the power to press charges and appoint counsel to defend the government in the President directly.