In the initial announcement, they had a picture of the old masks. Could they have been unsafe for the actors (poor vision, maybe)?
And again, I'm trying to think about time periods that people would want to see that could be touched. I get the feeling no one cared about gladiators--Classic Monsters and Graveyard Games grabbed all the hype. Vietnam is a no go, as is the Civil War. I know they got away with a WW2 zone back in 2009 but likely would not today. The Revolutionary War might be acceptable but I can't think of any house fitting environments since it was fought in all open fields.