How does a leader use body language to reinforce his/her leadership skills and qualities?
A good leader must demonstrate characteristics such as strength, courage, empathy, realism, idealism, listening abilities, as well as many others. However, a good leader can reinforce those characteristics by their body language and how they carry themselves. For example, a confident tone in their speaking voice, eye contact with others, respect for others, their stance, a firm handshake, the way they walk into a room, how they address others and physically maintain their composure regardless of the situation. To this end the leader demonstrates the full capacity of leadership skills.
The point that you are making here is perhaps in the area of 'Charismatic Leadership'. Whilst these kind of characteristics are valuable, they are not the be all and end all of leadership. The main aspect of leadership is really down to two words and they are 'honesty' and 'trust'. Without these characteristics, leaders are impotent - people will not follow people that they cannot trust implicitly and without 'followership' you cannot have 'leadership'. The interseting point in response to your question would be how can these characteristics be demonstrated through body language? They probably can't