I can't imagine why a repro broadcast sheet would be illegal. Why would they be any different than a repro fender tag? Repro window stickers are available from several sources, and they are not illegal. In fact I plan to get one of those made up for my car one of these days (window sticker). I have my advanced dealer shipping notice, so using the info off of that it should be possible to make a window sticker that is 100% accurate to what was on the window when the car was on the dealer lot.
If I tracked down the guy in AZ who makes the broadcast sheets I think the broadcast sheet would be a pretty close replica to the one missing for my car (I found 2 sheets for a later car in mine). I don't really see a great need to have a BS for that car since I have so much other documentation, but if I ever did desire to have one made for it to display with it at car shows, I'm not sure what possibly possess anyone to get their panties in a wad because of it?
I can see where any of these items can be used unethically, to try to pass a car off as having options it wasn't originally equipped with. But there is a big difference between unethical and illegal.