Maybe for 200x games or others, but for ATG, a Mopup While Leading will do nothing but see HAL have to bring in your Mopup While Losing in the next inning..........
I admit I don't play much ATG, but I usually set my 2nd closer as my 1st mopup, just to avoid the scenario you just described---and most DH ATG teams ride the starters hard anyway, I only see a downside for no-DH ATG, and then you could just avoid using the roll for ATG.