Pretty much everything I could've said in addition has already been said, I fully support this idea. It would be nice for POH's to finally have some more purpose.
I definitely love the first idea about the treasure chest/cape racks, and support it. I don't really know much about the dungeons thing though, I never really used dungeons even when I played back in the day. However, even though I dont know much about it, I support it as well, to see if people would like it and get POHs more use.
Sounds good ! We need more construction content. I support on the condition it is easy to implement and wouldn't be a huge update thus taking time away from more important updates.