This button should ignore stacks/units that don't have any legal moves left.
I believe the button already ignores units with 0 points left. But many times I have units that end up with 1 or 2 points left with no legal moves (ie 1 move on a plain or 2 moves in the woods/hills) and the next unit button keeps cycling to these units over and over again.
I realize it may be hard to handle cases with 2 or 3 moves left on hills/forest so I'd settle for just ignoring all units with 1 movement left.
KGb