Before I get completely flamed: I don't necessarily think this is true, but it would be interesting to consider this point of view

Duke has reached amazing offensive efficiency in recent history due to a four guard + one big lineup (at times with significant defensive cost). This is the first year where they consistently play a two big lineup. The advantages are in post play, rebounding, and paint defense, but a significant disadvantage this year is in floor spacing for our guards to drive.

A big part of the reason this forum thinks Grayson is taking such a huge step back this year is because there are always two bigs in the paint and he is driving a lot less. Similarly, Duval's greatest strength is also his driving ability. Thus my hot take is that going back to a four guard + one big lineup (ex. Duval, Grayson, O'Connell, Trent, Carter) may elevate the offense of our guards more than we miss the post presence of Bagley. Four Duke quality guards who can shoot, drive, and create would be a nightmare offensively.

I've also noticed that decent defenses do a great job to preventing the entry pass to Bagley, and we often just waste over half the shot clock attempting to get the ball to him. And when he gets doubled, he’s not that good at passing out of it, so he just dribbles to the perimeter and our offense resets. During the time we are trying to make the entry pass, most of our other guards just stand around on the perimeter. Perhaps a more motion-oriented offense would better suit them?

Perhaps the best offensive lineup is with Bagley instead of Carter as the one big, but the point of the big in this case is to just set screens and create for the guards, which Carter is better than Bagley at. And Carter can perhaps try an occasional pick n pop too.

tl;dr: A four guard + one big lineup would be better offensively than the current three guard + two big lineup, and Carter would be a better choice at the big than Bagley