Agreed with everything up to this point. Opinions, opinions, but for me every season of Williams' career has shown that he's a decent league 1 right back, but not good enough for the Championship. If we don't go up I'd hope he stays because he's the best we've got, but if we went up I'd be looking to replace him. I don't see either O'Keefe or Cotter having so much growth in them that they make Championship level. O'Keefe may make a decent L1 replacement if Williams goes.
I'm surprised more haven't gone for this option, it appears to me the obvious choice but we haven't seen McCart centrally yet but I think he has been our most reliable defender this season and could command the central position with height and decent pace either side of him.