What Shim said. I've already found some very nasty weapons made exclusively in ancient times, and I've already put some into my NS. Trust me, you don't want to see me running around with equipment made in the 15th Century, because my military's weaknesses will be so thoroughly mitigated by said weapons that I'll be playing a totally broken nation...

Which is something I don't necessarily want. And I know for damn sure someone doesn't want to be facing my guys when they've got stuff capable of messing them up more than it already is. Let's just keep it 5th Century. We're already bad enough at finding ways around things as it is.