I like Kellen Moore and hope he stays, but at this point we know nothing about how good he would be as head coach.
He has the same limitation Garrett had which is they come from one main offensive system and it would benefit him to either get better with that one system or gain exposure to other systems to take the best parts and improve his own system.
Yes, the Cowboys offense has been quite good this year, but look at all of the offensive weapons this team has.
You would have to think there are several offensive coordinators who would have done well with the Cowboys personnel and maybe one or two would have done even better than Moore.
If a team wants to hire him as head coach, I wish him well, but he is not irreplaceable as the Cowboys can find another offensive coordinator that can have success with the good players the Cowboys have and that is before improving in a couple of positions.