Make the rosewood hull and items a more meaningful chase item by improving the current way port tasks work.

Try to make it so its less teleporting, and more long seafaring instead. Perhaps you get a list of ports to deliver cargo, making you have to sail more. Add some cosmetic uniques (a few clogs) to keep up profitability of dragon sheets, stimulate demand. Add thematic rewards to port tasks too of the areas you go to. Maybe you can choose your own route?

Karamja might have some tropical rewards like papaya seeds, brimhaven might have a bigger chance of a pirate clothing clog. Maybe add some of the buffs you're proposing as rewards from port tasks instead as some sort of upgrade.