I think...although I am not sure the very idea that most of this movie takes place in the past, could be considered going in a different direction...esspecially for the general audience, who may have picked up one or two Cap comics in thier lives.... but may not actually be fully aware of his origin.
Seriously..think about it, Marvel characters have all been based on the here and now, Thor will based on an alternate dimension theory...but time still parallels present day earth, even if Thor is Imortal...but Cap..
Caps Origin..everything... is based on the WW2 concept.