Before everyone gets too excited, consider what they will actually allow through the gates and practicality. I think we need to aim for portable. In fact, I think we should have a couple/few and have a small scale battle. Remember, we need to be able to control landing areas, otherwise RenFaire will be very displeased with us.
I was thinking a Vitruvian Man suit, with extra arms and legs that move in symmetry based on a mechanism attached to the circular and square halo frames...
As I recall, my one big project idea when I joined i3 was the Gatling Trebuchet. Does that fit the bill for both "period" and "nifty"? Sadly, time, distance and gas costs forced me to allow my membership to lapse, but I'm happy to share my designs if anyone feels like picking up the ball and running with it.