Okay, this might be the craziest and most outlandish theory out there, but what if part of Blackbeard's plan for conquering the world and claiming the One Piece involves the complete and total destruction of the Marines?
Just hear me out: What if Blackbeard has members of his crew infiltrate the Marines, planting bombs in every battleship and Marine base. Then, after tricking the Marines into certain location, he triggers the bombs, destroying every base and battleship, killing hundreds of Marines, and cutting off the remaining Marines from additional resources. Then, he has his 'Ten Commanders' which he had strategically placed slaughter all that was left of the Marines while he himself attacked Marineford. After a grueling battle with Sakazuki, he grabs the Fleet Commander's neck in a vice-like grip through the combination of his Dark Dark fruit and Haki. Then he delivers a fatal close range Tremor punch to Sakazuki's face and steals his Devil Fruit before unceremoniously hurling his corpse into the sea followed by using the Tremor Tremor fruit to accomplish what he set out to do two years ago: destroy Marineford, all the while laughing madly.
What do you think? How outlandish would you call that theory?