Quoted from Ripper:
It's an interesting idea but I wonder if Infinity War would be too complex what with so many characters?
Unless they went the JJP route as they did with the new Pirates and had each Avenger, with his or her "special powers", as a selectable character to play as. Just as JJP Pirates spans all of the Pirates movies so too could the Infinity War pin span the entire Marvel Cinematic Universe. Could be epic.