I am saying the other way round,until luffy is on an admiral level like Kizaru ,he has no chance against big mom .Bad argument.
They were already doing that even before Luffy crash-landed in Marineford. He's not stronger than most VA's before the Time Skip. It's only the lack of feats against them that suggest that they're weaker than Luffy, yet we see that they're Rokushiki AND Haki users, same thing that Luffy is. Momonga takes it even one step further and uses a sword. Doberman has a Dalmatian Zoan.
Unless Luffy lolstomps Big Mam or something like that, he's not reaching Akainu and Kizaru's level.
DO not forgot luffy was continuously fighting in Impel down ,all he had was 3 to hours rest to marineford .Ivan had to use the emergency hormone on him twice ,that was his condition .He was already exhausted from his continuous fighting . Do you really think that dalmation guy was more exhausted than luffy .how many guys that the dalmation guy fight ? but there is ample evidence to support that luffy took down several vice admirals even while he was not in his full strength and over exhausted.