Oh...If you aren't familiar with the Coen Brothers, you should be ashamed . They are the creators of Fargo, Raising Arizona, The Big Lebowsky, O' Brother Where Art Tho, and a handful of other, brilliant movies.
Hey I don't like them much either, but he is just a supporting role. I think the reason they suck so much is because of the writers behind the roles the wayans brothers play. With the Coen(there's no "h" btw) brothers doing the writing and directing I think he won't be too bothersome. I didn't think Marlon Wayans hurt Requiem for Dream, for instance. It wasn't a uber acting job, but it didn't stand out as something that hurt the film.
Also, I don't think his role in the film will be bigger than other members of the group of criminals under Tom Hanks, but I think he gets a lot of time in the trailer because he is familiar, compared to, Tzi Ma or Ryan Hurst, whom of course noone recognizes by name.