What are some POH upgrades you could see fitting in the game?

I think jagex should consider rare items that can be used to make cool upgrades to your poh, similar to how sailing does it with the bottled storm, etc. It's not really been explored before in osrs. What are some poh upgrades you could see coming to the game that are useful but not overpowered?

I think a bank deposit box would be cool. Doesn't really break anything but would be a nice little feature to have in your house. Full banking would be too op.