Porygon-X seems nothing like a defensive Pokemon. It is just kinda better Porygon-Z.
Pokemon: Liepard
Typing: Dark / Poison
Abilities: Prankster / Limber | Unburden
Stats: 106 HP / 64 Atk / 88 Def / 50 SpA / 88 SpD / 50 Spe
Movepool Additions: Toxic Spikes, Baneful Bunker, Clear Smog, Poison Jab, Binding Vow
Movepool Removals: N/A
Reasoning: Imo, a bulky Prankster user without Recovery is the best way to accomplish Binding Vow while still remaining a balanced concept, because lets be frank, if it can easily heal itself of the damage sustained during Binding Vow this Pokemon can quickly spiral out of control. As is, I just swapped around Liepard's stats and added the Poison typing so you can't try to Poison it.
Pokemon: Stakataka
Typing: Rock / Steel
Abilities: Adaptive Armor
Stats: 131 HP / 53 Atk / 73 Def / 41 SpA / 61 SpD / 211 Spe
Movepool Additions: Leech Seed, Jungle Healing, Rapid Spin
Movepool Removals: Body Press
Reasoning: Very, very, very fast wall. Stakataka shapes up as an annoying presence to face being a defensive Pokemon that is absolutely the fastest thing that will ever be in the mod, letting play a very different playstyle than most common "speed control" options. Its held in check by its typing that has a lot of shoddy weaknesses like Fighting, Ground or Water, and even if its tye fastest SubSeeder in existence, it can't do much against Pokemon that eat it up.