Idea for if Porky gets added to smash: Lucas deals more damage to Porky while in battle and Porky deals more damage to Lucas
I assume you mean as a fighter and not a boss like how he was for Brawl.
I honestly do not know how they could implement this into Smash since it's very character specific but!- How it could work is Lucas's fighting style is easier to combat Porky. Whatever his moveset may be. I always imagined Porky to have an opposite fighting style to Ness and Lucas. Since they are PSI users, he'd probably depend on tech and have shorter ranged attacks.
I love the concept of bringing Porky in as a fighter or back as a boss. Tho considering their track record with Mother rep... Yeah... No... Goodbye Porky Minch trapped in your capsule forever lol.