Going from prototype photo's, as a layout model, that looks fine, the slats, (front bar of the louvres), cover up most of the hole, and the black backing finishes the job off.
In order to give the louvres a bit of 3D relief, would it be possible to leave the bit of brass in between the slats, etch it through on the two sides and along the top, then half etch the top of the slat on the inside and fold the bit back in at a jaunty angle to give the impression of a louvre?
I realise that this is a monumental task with the number of louvres involved, but, having got used to the millions of rivets on the coke hoppers, shouldn't be too onerous a task.
Mike.