Body physique is the hardest thing to change of all the aspects, so if one has this problem, you need to focus on other aspect.

Napoleon Bonaparte is short, but he was not only a leader, he was a conqueror. Tyrion Lannister, even though fictional, is another example, learn the actor's performance, how he use his face and voice.

Learn psychology and interpersonal interaction, think of it as problem solving using human for human problems instead of your usual tool of choosing.

Learn how to command with charisma. Use visual, sound, and tactile as optimum as you can. For those who see persuasion and manipulation as immoral, get rid of it. As long as your intention are good, you'll use those weapons carefully.