So tell me, all you people that wish some awesome 10k cargo trains. Making one VIP to Kurile run that would make you spend 10mil to begin with to earn 40, how much should I as a pirate tax you? 15mil? 20? Can I ask for 30% of your goods? Trains with huge cargo hold would bring radical changes trough the game. Maybe positive, maybe negative, I don't have experience to tell. But those traders would certainly need escorts, and those escorts would certainly ask for plenty and to end it, profits would be the same.
The diamonds - nob run is fine, you just need more pirates on it. You'll see how would the trade frequency drop then. You can make 10mil every half an hour easily, just sitting on a hole and charging one mil or even half a mil every time trader passes.