9. Jon Grissom
Ever heard of Lyca, the dog we fired up into space to make sure the moon was okay for humans? Well, Grissom was the human equivalent for space flight in the ME universe, volunteering himself to travel through the first Mass Relay discovered off Pluto and communicating whether he still had a face or not on the other side. Luckily he did, and such began the human foray into the Systems Alliance. But first was the crippling First Contact War which also saw Grissom take a leading role, until following all this Shepard-like publicity as the man everyone's pinning their hopes on, he ends up becoming a recluse, retiring to a life of isolation on planet Elysium. Getting into his mind and fleshing out (or seeing) the events of his life are a major part of the human struggle in the series, and it'd be a way of doing another Zaeed-like mercenary but with a far more interesting tale to tell.