Complete restructuring of how and why people get promoted, phased in over 30 years. Some of the most incompetent, uneducated people are in charge right now because tenure. I've dealt with Corporals who are so fucking sharp and attentive, whereas Captains can't read or tie their shoes, but simply waited out the military clock for a better position and better pay. This might sound like an elitist attitude.
I would also couple this with stomping out all the "Old-school" attitudes. The sexism and racism can be removed, while still allowing swearing and tough love. Fortunately, this seems to be getting better. Many more educated people are entering the military because they can't find work. Say what you will, but education WILL combat any natural or learned biases.