@uniaka:
But based on that all 5 yonkou allies are easy targets for marines, yet we don't hear about marines capturing them. While the main 10 men crew has too much to deal with, the grand fleet is not there so they can assume they will jump to help or the capone pirates and fishmen allies. And wano could just last 1 day like dressrosa so things can get better for SHs fast.
The problem with this statement is that the Marines aren't always held at bay just because someone is associated with a Yonko. The Pinkbeard Pirates waited until the stronger Marines left for Reverie before they pillaged Lulusia Kingdom. No matter how much clout the Straw Hats' flag might give Germa, it still carries the expectation that the Straw Hats will come to back up Germa if they're overwhelmed. That expectation cannot last forever and Germa would eventually become exposed since the Straw Hats would never help them. It would be like Usopp's lies about an 8000-member crew backing him up; the Germa might have the crew, but they don't have the backup.
Even a good threat of a Yonko's interference doesn't always stop the Marines. They were willing to go to war with Whitebeard just because they believed Ace was too dangerous to let live. They're very inclined to interfere with any interaction between the Yonko since a possible alliance between them could tip the balance. I heavily doubt conquering an entire Blue would be something the government would tolerate, so it is absolutely necessary for Luffy's crew to be willing to flex their muscle if Germa wants any chance at making a serious raid on the North Blue.
And that's not even getting into the fact that most of Luffy's clout is based on Morgans' newspaper report and we still don't really know what the government thinks about it. I would be surprised if they were onboard enough to think that the Straw Hats could go that far. Luffy still hasn't proven a match to the admirals yet.
@Screwtape:
BTW It's a dang shame that Meme needs to team up with Kaido to take out a rookie. These are suppose to be the four most powerful pirates in one piece world?
Big Mom explicitly said that she would be the one to kill Luffy. Whatever her meeting with Kaido is about, it's not gonna result in a teamup against him.