Yes, let it all come back, even the legendaries like the staff from classic and the challenge mode sets from pandaria that you can’t get anymore for transmog.
You can still make them rare as heck to drop and obtain them, just bring them back
But honestly people just want to have a shiny badge of prestiege and be like “ha ha, you didn’t play as long as we have because we were blessed with internet while we were younger, You want these, well too bad, you’ll never have 'em.” screw that mindset tbh