These both sound like excellent ideas, the sort of thing I've been watching the forums for and never seen organised! I like the suggestion of making the client Brettonia and requiring things that can be only found in Kusari, because like you said, if it's a Brettonian company with the contract they may have to use sub-contracting to get them, meaning Hector can cut himself a slice of that pie! He does advertise himself as a blockade runner after all!
EDIT: loogas, the main depot for the items could always be a shared ship, with 3-4 vouched-for people across timezones. This is more complicated though, so office hours might be best, be still runs into a problem for people outside of it's time-zone. Then there's the depot itself. Would the third party be allowed to attack THAT? Seems to me they should be able to, after all you would attack it if you found the opportunity to. Why pick off traders when you can let them do the hard work and then attack one large target? This means that the depot would have be positioned with this in mind, and maybe even force the depot to have to relocate every so often, just to keep people on their toes a little bit more during the week, as the traders would need to keep in contact with each other to pass on the location, and the pirates would be able to mix things up by deciding if they'd rather disrupt the supply, or destroy the supplies at it's source.