I have given valid alternatives in my first post here. We have met a few civilians of various professions that have had combat training yet are not military.
Liara is an archaeologist.
Amanda Kenson is a scientist.
Mordin Solas is a doctor and scientist(While he served in the STG he wasn't a frontline fighter like say Kirrahe and his men are).
The people of Feros were a variety of professions from colonist to rent-a-cops.
Then of course there are more mercenary professions.
So according to the MEU, you can be quite a number of things that have everything required without being part of the military.
Not true actually. Throughout history there have been many people who have shown skills with combat leadership without them having a military background. Or cases of fresh recruits and trainees who have never been in a combat situation before yet have leadership abilities shine through. With us being a protagonist, there is nothing hard to believe about that being part of what makes the protagonist special.
Liara would rather stay in a dusty ruin or run a network from the shadows than actually get physically involved.
Amanda Kenson worked for the military as a scientist
Mordin Solus worked for his governments version of MI5, he was trained by the military and was once part of the military
People of Feros where being stomped into a puddle before Shepard turned up, the people that stiffened the resistance was ex Alliance military.
90% of most mercenary companies are made up of ex military ( seriously would you hire a merc company that was made up of ex Walmart and Starbucks employees)
Please list some of those historical so called leaders as most of the ones i know of were convenient figureheads.