How many rounds? Chalres lacked a good heavyweight chin, and liked to brawl, so Williard has a chance here. I'll go with Charles via UD.
Charles beats the **** out of him. Willard might be on his feet at the end but he isn't going to look too terribly pretty, considering how well Charles could combination punch.
I like Charles at any distance under 25 rounds and one-sidedly. If it is a finish fight such as the one with Johnson, Willard might outlast Charles. The problem with picking a finish fight is that Charles never fought that way, but I see no reason he might not have had the stamina to go a long ways and maybe even outlast Willard. It is all speculation.
If scheduled for 12 or 15 rounds, a prime Ezzard Charles would beat a prime Jess Willard, by unanimous decision or late stoppage...in my opinion.
Tell that to Marciano, Valdez, Louis, Ray, Moore, Wallace, and Satterfield. I bet they all would say Charles had a very good chin. I really dont think you have charles style figured out. In charles prime, he was hardly anything but a slick boxer who would use a stick and move style and had great footwork. he was a defensive counterpuncher watch some of his late 1940s fights.
I actually think Charles has a good chance of stopping Willard. Charles wasn't a huge puncher at heavyweight, but he wouldn't merit the moniker "the Cinicinatti Cobra" if he didn't have some power, and he tended to stop durable brawlers with good chins. Charles by UD or a TKO due to cuts/accumulation.
Oh God, Jess is so far out of his league here, we have to create an entirely new league just to find some place to put him.. Charles by one-sided whoopin'