Hi i have a idea for a anime or manga?

ok its set year 2049 world war 3 more than 1 billion people were killed and all of the mechas were killed and whats left of the sides are no splinted in to factions and there but it will follow 3 people wan the main guy don't know his name yet will betray hi faction to save a young boy and girl because he reminds him of his little brother who he cod not save so now they are looking for a way to stop the faction from wiping out the la (liberty army) and to do that they need to find the main guys mecha and find a way to power it to save whats left of there land