This is a very big positive.
If he's smart, Johann will measure the skills of each player in the key areas of the game as well as review the use of those skills in Mosconi Cups past: a) the break, b) pocketing, c) pattern play, d) defense, e) kicking/jumping and f) strategy and two way shots. He could then advise them of where development is needed. Those who don't do anything to develop the skills in which they are advised of deficiency should have it count against them when the final selections are made.
Making the players more accountable for managing their own development in areas of deficiency would be a new approach, an approach whose time has come. Displaying the exact same weaknesses year after year is a Team USA problem that, in my view, remains unaddressed. Team USA will have to do a lot more than shoot straighter to be successful.
There's one more "measurement" you left out Stu, how to handle the pressure of playing in the Mosconi Cup. That should be on the top of the list! I will say once more that the mental side of the game is equally important as the physical side, especially at the elite level.