I really don't see why Luffy would win "easily" Those admirals have been around for quite some time. They are send to take out the strongest pirates on the seas. People like Whitebeard and all his commanders even had a though time fighting him.
Look at the Lucci fight. He was "just" a tiger, No need for haki there and luffy nearly got himself killed.
If Akianu touches you, you melt
If Aokiji touches you, you freeze
Kizaru is as fast as the speed of light
There is nothing that indicates a walkover for Luffy in fact I still think he is far away from beating an admiral, even with the overrated haki.
