The league title should be decided by each team playing every other team an even number of times. This change would abandon that fundamental principle as the games would be an additional round with a draw deciding which teams played each other. Just imagine if a tight title race was decided by the fact that Manchester United thrashed Derby in the overseas round while Arsenal drew with Chelsea.
American sports mix an element of league and cup play because in American football, baseball and basketball there are no separate cup competitions. In English football there is and so the two should remain separate.