This may actually be in the server and I've just never seen it, but I was thinking how cool it would be if you could carry very heavy pieces of a siege equipment(you'd need strong people of course to do this) that you can then set down on the ground wherever you want. Then someone with a good engineering skill could use the pieces and assemble the catapult on the spot(this would take some time, say 10 rounds-ish). Then you have a mobile catapult. I was thinking of how cool it would be to do this on the Stargazer quest where you storm a castle, to 'siege' the castle rather than everyone metagaming the back entrance and railroading 50+ goblins (which turns the castle into little more than an obstacle and framerate reducer)
It does exist, DMs have on occasion provided "catapult kits" that can be activated to place a catapult on the ground. They weigh ~200lbs. They aren't available for general use though.