Now I'm not actually posting this to annoy people who are into using the exploratory missions to make Gil off of. I'm going too anyways because it's an elegant solution and the work around for how you submarine people will try to keep in fuel is just hilarious to me.
Solution: ceruleum fuel becomes untradeable.
This limits it to just that fc able to get fuel for their subs or airships to be sent out. This could also be a way to liven them up too as pretty much all these fcs are solo owned.
What's the workaround to this. Easy. Put an alt in the fc who can carry the fuel to another fc you own or someone else's you are selling too.
The fix for this is to have a cool down between leaving a fc and joining a new one. Say 72 real hours.
I can keep going but this probably annoyed enough people and I was mainly posting it because I had seen another topic about those that utilize voyages as income.