Perhaps it could be used as a shrine or temple of worship where your followers give thanks to you for taking them to a new land instead of being a place where they sacrifice themselves? Instead of just gems, it could perhaps give you belief, grain, ore, and gems. The amounts of each you get can depend on how many followers you leash there.

I'm not saying that this will happen, mind. Just giving my own ideas as a player. :)

Ark of expansion. Burn it to the ground to open up the map. Please remember not to burn it while there are followers inside.

yeah, because then they'd run around with their heads on fire, spreading it to all the trees and houses (and other people) on the map.

I'd love to see the ship being used, once you meet the Meanies, on Weyworld.
Your people could start to strip the ark down and use the materials to wage war by making trebuchets, trojan horses and arrows or perhaps use it to befriend them by making gifts from the materials?
A trebuchet/catapult would be cool though, I think. It could actually be a replacement for the sacrificial temple, in that you would sacrifice your followers by flinging them at your foes, instead of rocks! :)