Idea is that a man is in a suspension pod. He goes through a "dream-like reality," Why? This is so he will wake up ready for reality (think as the futures replacement for schooling.) This could lead into interesting problems like what would people not raised on reality "wake up" to, (I think of rick and morty with the perfectly level area reaction we get from morty.)
The protagonist will have some sort of adventure. They could start out as a person who dots on their family, and then gets everything striped from them by a "war" that takes place in this dream. Through the loss of loved ones he will go through the military to get his revenge. Through this revenge he will find talent in piloting mechs. This revelation should then have some not all info about the proportion of the population that is can pilot them, and other mech information. Then the need for action will bubble up from the citizens, and so the "good," (could be either) government will take action in this war pushing forward the recruits (including protagonist.) This starts bigger arc of the beginning where many battles take place. These battles show the protagonists talent in piloting slightly above average but not enough to win against numbers (no Mary Sue here.)
The main character needs to have mental weakness from losing his wife and kid (maybe even friends.) This can manifest in hallucinations, anger, his willingness to push others way, and to accompany these moments there should be a flash back to show what he was like before to contrast with after, (invoke the pathos.)
They will be guided into a "direction of redemption," to move the plot, and to give readers a sense of direction. This should come after the mobilization of the recruits. His Fate will challenge him to a duel between his families killer and himself. He will give up everything he has left to fight this mighty foe. This climatic battle will end in a Pyrrhic victory of he gets his revenge only to die moments after the battle ends. This concludes his time in the pod.
He will reawaken with scientists moving all about. He then has a scientist walk up to him, and examines him. They then will start explaining what has gone on, and why he is there. This explanation shatters his already fractured mind.
Continue?