Suggestion from The Flying Fox on Arwing Landing:
"What you could do, is incorporate a few battles that would chronologically take place before the SF games and after them. Kind of like, help Corneria conquer Titania (perhaps it was under wolven/venomian rule before? :3) and if ya win, you play on Titania later on as a defence mission, if you lose, you need to conquer it later on or something. Winning in the pre-campaigns give you bonuses like better armor and weapons or something, and winning on the same level in the later campaign earns you a medal which will give you bonuses."
Some interesting ideas, but the whole pre-campaign thing might not fit with our current story.