Why are you required to commit to a full stop landing if reverse thrust is selected?
The biggest problem is that thrust reversers take time to move. During that time they are still producing reverse thrust (even if only at idle) and slowing you down. They must all completely close before you get forward thrust and can add power to start accelerating again.  Then, what happens if they don't stow, or only part of them stow?  Now you've used up valuable runway that could have been used to stop (or at least slow down more) and are no longer in a position to takeoff from. The consequences can be pretty severe.