I would disagree with McVay wanting another to completely run the defense.
McVay through the hiring of McConnell has someone to do the majority of the work of running the offense. My thought here is that McVay wants to be invested in the defense and special teams--moving from more of an individual contributor role(running offense) to a managerial role(overseeing and enhancing the offense, defense and special teams),
Staley was a special case for McVay. With Staley McVay actually hired someone to not only run his defense but teach him that system of defense. Given Staley's departure and the return of McConnell I would expect McVay to be heavily invested in the defense this year. Stafford's arrival will certainly keep McVay focused on the offensive side. But McVay, clearly to me, wants to run the 2 high light box match zone system Staley brought to the team moving forward.
Great question--I will be greatly interested in learning what McVay spends his time on throughout both the offseason and training camp.