Why would Luffy require G5 for Big Mom? Stop with the rewriting of the story...
This was said about G2/3 Luffy btw, forget G4, forget G5.
This after Big Mom fought Kaidou recently.
Did you skip over the entire Kaidou fight, where Luffy was able to go toe to toe with him? Forcing Hybrid Kaidou to drink
pre G4. Big Mom cannot keep up with that pace, G2/3 Luffy will embarass her, even moreso since he is immune to lightning. He started to dodge Kaidou's top speed and eat advCoC attacks for breakfast, wtf is Big Mom gonna do here combatwise to Luffy, with her lightning taken away to boot??
He can fight in g2/3 forever, landing thousands of attacks, each one fucking her up badly as they were with Kaidou. And then he uses a round of G4 for good measure to end her for good.
There is zero chance Big Mom survives all out pre G5 Luffy, feats and canon statement have cemented this. There's no angle you can come up with to convince any sane person who closely followed the wano battles otherwise.