I wouldn't know. I know you can use it to ferry others around to places they would never have visited on their own because of the large distances, but tbh - I'd rather prefer that to be a single player option. I'm not hot on begging others for something I'd like to do or get ripped off because they have the means but me peasant doesn't. In essence - I don't really want to play Elite as MP game.
If you think having player made trade offer for good money, taxi services to distant part of the galaxy, good transport to help you do CG delivery, quick repair/refuel/rearm near a CZ or in deep space... is griefing, then yeah, nothing can be done.
If anything, FC are harder to use to grief than any other tools the player have. At worst, they grief amongst each other because FC never prevented a regular ship to do whatever he or she wanted to do.
It's probably a lot of work, but I've suggested that the info panel in the system map would be a great place to give a FC owner some space to insert a description of services/prices/etc..
What could have been done :
-ability to "sub" (and unsub ofc) to a FC (or several) so you get to know what they are doing, where they are, what they plan to do.... Say, sub to the Colonia taxi service, so you know when to take it. Or PTN booze cruise. Or your minor faction FC.
-ability for FC owner to set up a message that is transmitted to all player "subbed" to his FC and everyone currently on board, like "leaving for XX system next".
-ability to plot several jump at a time (basically what the regular ship can do), with the extra ability to set a timer between each jump, so you can plot exploration expeditions in a few click. Have all the datas concerning the trip in a handy and easy to access tool (like megaships currently do), so the player know they have say 24h before the FC jump to the next system (with the name and all)
-A "board" of some kind the FC owner can personalize. Perhaps with pre made tag you can pick from (role : taxi, refuel, trade, CG hauler, exploration...). With a search feature to search for FC (and pre made filter like "all access, no tariff, search for installed modules...). Say for example "FC dedicated to colonia-bubble taxi" and then you search for taxi, and voila. Essentially, like the faction search but for carrier
-ability to set up whitelist and blacklist for carrier owner, with what kind of access they give. Say I don't want CMDR Bob aboard because I don't like him, so he is blacklisted and will never be able to land on my FC. On the other hand, CMDR Bill is my pal, and even if I'm not ingame, he can land and access the "VIP" observation deck. As for CMDR Jim, that's my alt, so I want to give him access to jump capabilities as well. All that irrelevant of the regular "open for all-friend only-closed" status we already have
-make it clear which FC can be landed upon. We have already an icon to let you know if you can land on station (especially if they don't have large pad and you are a large ship), use that one ? Seems obvious to me.
-ability to reserve cargo space for some people. For CG hauling for example. Or have a "private storage" module which allow CMDR to store some amount of commodities. If the commodities is left untouched for a set period of time, the CMDR is warned, and if they still don't do anything then it's transferred to the FC owner. Make it so having stored stuff on the FC gives you access for as long as you have stuff inside to prevent abuse.
From the top of my head, can be worked upon, balanced and improved. They have a dev team for that^^