Show of hands: Who here thinks that Player Owned Port mechanics make it a legit method of obtaining the highest level armor currently available in game? I know many feel that high level armor and weapons should only come from boss monsters. However, I've argued that if you have a method that requires multiple high level skills, a bit of luck, a lot of time and/or tediousness then even non-combat skills can be a great way to create player made high level armor and weapons.
I'm sure that trade goods will be more available to players that get to the last area and have maxed out crews. However, I'm also going to guess that special voyages in the 6th area will never be 100% so you're always risking some kind of loss on top of having the luck of a special trade goods voyage pop up. It's a balanced method akin to camping Nex with regards to creating high level gear. I hope that Jagex keeps releasing other methods that plays on this concept (flasks and bloodwood trees for example).
The game is quite messed up. The system should be - the combat related characters fight bosses for materials (dragon scales and whatever) and after that they trade them to skillers who make the armors and weapons. This way both the combat characters and the skillers would profit (a skiller wont be able to make an armor/weapon without the materials so he'll need a combat character to get them and vice versa - the combat character wont be able to make the armor on his own).