I was thinking more of improvements like treadmill jolly roger shark and others, i would be good if we could sell them like sketches for 75% of their value and be able to use the currency on other improvements.

so you could change the look of your haven and they could put up special themes in the improvements like they do at Christmas with the trees.

could they not do a special once a month allowing you to change improvements.  That would be easier to program in .

A bit like they do with the haven upgrades offer now, just add in a swap feature within the package ?

Hello, Captains! 

From time to time we do special themes and make new Improvements. But unfortunately, we can't do it very often as it requires much time and efforts of our developers and designers.