I've done some research and I'm aware that the Soldier Generation Variables in gameconfig.xml would modify stats for all soldiers, but I'm really looking to modify only a single soldier's stats. Whether it can be done on the fly in-game or through a more complex method that requires a new game isn't a concern to me.
I've also heard that you can hex edit a soldier's stats in a save game, but I'm not too experienced with hex editing; still, it's an option I'll take if I must.