- make Hancock and Kuma secretly strategized together, after a series of meetings and recognizing that they both have affinity to Luffy and his family (Hancock's care and Kuma's Revo background). Hancock hypnotizes the crucially-located marines like Ace's executioner, key holder, soldiers surrounding the execution platform,
with Mero2. Kuma plant hundreds of Nikyuu2 landmines in Marineford, Admiral and Execution Platform, ready to explode whenever ready.
- Hancock secretly persuades Garp to, if not directly participating in combat to protect Luffy, at least not actively participating to capture Luffy. She brings out her secret about Celestial Dragons etc and appeal to Garp with it, triggering Garp's grandpa paternal instinct.
- Kuma bribes both Vegapunk and Doflamingo with some Revo weaponries, artifacts, valuable information about location of secret treasure vault in Marie Jois, or rare blueprints to make strange or artificial DFs, etc. The condition is Dofla have to control multiple high-ranking marines like VCs to seemingly betray each other, causing riot using Parasito or String Clones. And Vegapunk is to temporarily give the control of all Pacifistas to Kuma. Just temporarily, not permanent, itll be more luring to Vegapunk.
- Kuma contact Revo to dish out strong armies to help like Sabo and multiple divisions, possinly Dragon himself if Sabo and Kuma play the brother card right. Hancock contact any female pirate crews they can find, maybe including even Fishman Kingdom and persuading Shirahoshi, or even bribing BM with something. Rare candies etc. Poseidon and BM just have to sink Marineford to the sea, dont have to protect Luffy specifically, but Shirahoshi will surely protect Luffy once Luffy cast his magic on her.
- make Luffy undergo basic CoC Awakening Impel Down when against the wolves to carry-protect the previously-tortured Jimbei or something, but by receiving the hints from Jimbei who had witnessed WB's battles, Luffy tried to figure out the CoC-tech formula and levels, constantly increasing how much he can infuse to his attacks, and actually managed to attain CoC Coating during Impel Down escape's final battle against Magellan, beating Magellan with it.
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Those are key points i can think about